American Airlines Flight 320

American Airlines Flight 320 was a scheduled flight between Chicago Midway Airport and New York City's LaGuardia Airport. On February 3, 1959, the Lockheed L-188 Electra performing the flight crashed into the East River during its descent and approach to LaGuardia Airport, killing 65 of the 73 people on board. Weather conditions in the area were poor, and the aircraft descended through dense clouds and fog. As it approached the runway, it flew lower than the intended path and crashed into the icy river 4900 ft short of the runway. American Airlines had been flying the newly-developed Lockheed Electra in commercial service for only about two weeks before the crash, and the accident was the first involving the aircraft type.

After the crash, surviving flight crew members said that the aircraft's instruments had indicated normal and appropriate altitudes right up to the moment of impact, but eyewitnesses who saw the aircraft from the ground said that the aircraft seemed to be flying much lower than what was normal for planes approaching the airport. An investigation by the Civil Aeronautics Board concluded that several mistakes by the flight crew were the cause of the crash, and the flight crew's inexperience flying the type of aircraft, and poor weather conditions were contributing factors. The Air Line Pilots Association disputed the conclusion, blaming the accident on faulty instruments in the aircraft and on poor weather conditions, not on any mistakes made by the highly experienced flight crew. The lessons from the accident led to new regulations requiring flight recorders in large passenger aircraft, and to new construction at LaGuardia Airport to extend the runways, improve approach lighting systems, and add an instrument landing system to the runway that was involved.

Background
Flight 320 was a regularly-scheduled flight between Chicago and New York City operated by American Airlines using one of the company's newly-obtained Lockheed L-188 Electra turbine propeller aircraft. The airline had first started flying the Electra in commercial service on January 23, 1959, and it offered six daily round-trip flights on its route between New York and Chicago, with plans to deploy the new aircraft to other destinations once Lockheed was able to deliver more. The new planes, which carried seventy passengers, were faster than the company's Douglas DC-7 aircraft that it had been using on the route, and shortened the flight from Chicago to New York by half an hour.

On the evening of February 3, 1959, the flight was scheduled to leave Chicago's Midway Airport at 9:00p.m. EST, but wind-driven snow delayed its departure. The flight was eventually airborne fifty-four minutes after it was scheduled, and was one of the last flights to depart Chicago that evening before the airport was closed due to the storm. Sixty-eight passengers and five crew members were aboard, and the trip was expected to take one hour and forty-two minutes. The flight to the New York City area was uneventful, with the aircraft cruising at 21000 ft.

Accident
At 11:34p.m., the flight approached the New York City area. The LaGuardia Airport approach controller advised the pilots that the weather conditions at the airport included overcast skies with a ceiling of 400 ft and a visibility of 1.25 mi. The controller instructed the flight to proceed to the north of the airport, and to prepare to perform a direct approach to Runway 22 over the East River. At 11:55p.m., when the aircraft was 2.8 mi from the airport, LaGuardia tower controllers gave the flight its final landing clearance for runway 22. The flight crew acknowledged the clearance with a simple acknowledgement of "320", and there was no further radio communication. Moments later, the aircraft, flying at 140 knot, struck theEast River about 4900 ft short of the runway.

A witness working on a nearby tugboat said he saw the aircraft flying very low over the river before it hit the water with a very loud noise. A different worker on the tugboat also saw the impact, and said that it looked like the aircraft hit the river with a nose-down angle. A witness in a car approaching the Whitestone Bridge described seeing the aircraft pass overhead only about 100 ft above the ground. He did not notice if the landing gear was down but he said he could see the whole underside and the lights in the windows of the aircraft. Surviving passengers and crew members in the main cabin said that the descent prior to the crash seemed to be uneventful and routine. Many residents in the area said they heard the Electra fly overhead and that it sounded like it was flying lower than planes usually did in the area.

The accident was the first crash involving the Lockheed L-188 Electra aircraft, which had begun commercial service at American Airlines in the previous weeks. It was the first significant accident involving an American Airlines aircraft since the crash of American Airlines Flight 327 on January 6, 1957.

Aftermath
A privately-owned tugboat from New England was on the river near the crash when its crew saw and heard the impact. The crew released the barges that the boat had been towing and headed to the crash site. The tugboat was the first to arrive at the scene, and the crew lit up the area with the boat's searchlight. Everyone who survived the crash was rescued by the crew, including one man who was pulled up from 4 ft below the surface of the water. Two police helicopters and at least a dozen boats from the Coast Guard and the New York Police Department arrived minutes later. In the darkness and the fog, rescuers could hear the cries of survivors, but poor visibility and swift river currents made recovery of the victims of the crash extremely difficult. Responders and nearby residents in the area heard shouts for help from locations further downstream from the crash site.

Public safety agencies set up four rescue stations along the river to evacuate survivors. Ambulances that were taking injured victims to hospitals had a hard time driving on the icy roads. Survivors were taken to Flushing Hospital and Queens General Hospital. Two temporary morgues were also set up on opposite sides of the river to receive victims as they were recovered.

By 5:00a.m. the next morning, at least 9 survivors had been rescued, 22 bodies had been located, and 39 other victims were still missing when the high winds and driving rain led to the decision to suspend the rescue operation. One of the survivors who had been taken to a hospital later died of her injuries. The New York Red Cross furnished supplies of rare blood types to aid the victims of the crash. Bodies that had been recovered were taken to Queens General Hospital for identification with assistance by agents from the Federal Bureau of Investigation and 25 city detectives. The agents used fingerprint records from its immigration, personal identification, and war service files to help identify the victims. Autopsies on twenty of the bodies revealed that the victims had died of crushed chests and broken necks, showing the force of the crash.

During the crash, the fuselage of the aircraft had broken into several pieces, but a 20 ft section of the aircraft remained in one piece. After two hours, 3 ft of the tail of the aircraft was the only part of the aircraft that was still visible above the surface of the water. Searchers on boats and on the shore picked up plane debris, personal belongings, and mail from the plane.

In Washington, D.C., the Civil Aeronautics Board (CAB) dispatched two investigators as soon as authorities became aware of the crash, and ordered the airline's records to be impounded. An additional team of 25 investigators was assembled and dispatched later the next day. The team was given the task of investigating all aspects of the flight, including the weather, flight operations, engines and propellers, flight instruments, and aircraft structures. Queens County District Attorney Frank O'Connor also started an inquiry about how the rescue efforts could have been improved, telling reporters that more passengers might have been rescued if there had been a system of rescue boats available to serve the city's two airports. The House Interstate and Foreign Commerce Committee asked the head of the Federal Aviation Agency (FAA) to report on the accident in a closed session in the days after the accident. After the two and a half hour meeting, it formed a special House subcommittee to investigate the crash and the overall safety issues raised by the transition to jet and turboprop aircraft.

Days after the crash, newspapers reported that there were safety systems that could have helped prevent the crash if they had been in place at the airport. A representative of the Air Line Pilots Association said that a system of flashing lights known as the Electronic Flash Approach System could have helped the pilot judge his altitude, if it had been present. The association also called for the installation of a more comprehensive instrument landing system that would have provided altitude and horizontal guidance to flight crews landing on runway 22. The system in place at the time of the accident only provided horizontal guidance, although such a system was already installed for the same runway for aircraft approaching from the opposite direction. At the time, there were only two airports in the United States that had such a system installed for approaches on both directions of a runway. At a meeting on February 5, commissioners of the Port of New York Authority explained that the installation of such systems on runway 22 was considered to be very difficult because the approach lighting system would block the waterway used by ships to reach docks in Queens.

Aircraft
The aircraft was a Lockheed L-188 Electra turbine propeller aircraft, serial number 1015, registered as tail number N6101A. This was one of the first Electras delivered to American Airlines, and was named "Flagship New York". Construction had been completed by the Lockheed Aircraft Corporation on November 27, 1958. At the time of the crash, the aircraft had flown for a total of 302 hours. It was powered by four Allison 501-D13 engines.

Promoted as an efficient, fast, and profitable aircraft, the Electra was the first turbine propeller aircraft to be produced in the United States. The first plane was delivered to Eastern Air Lines in October1958, who began operating commercial flights with the aircraft on January 1, 1959. American Airlines took delivery of its first Electra in December1958, and its first commercial flight was twelve days before the crash. After the crash of American Airlines flight 320, two more Electras crashed in the following months after suffering catastrophic structural failures, killing all of the occupants. Braniff International Airways Flight 542 crashed in September1959, and Northwest Orient Airlines Flight 710 crashed in March1960. After extensive research, Lockheed identified and corrected a flaw in the engine mounts which had been the cause of the structural failures of the other two crashes. However, the negative publicity surrounding all of the accidents within a short period of time led to the loss of public confidence in the safety of the aircraft, and only 174 were ever produced.

Passengers and crew
The flight carried 68 passengers and 5 crew members, all residents of the United States. Of the 68 passengers, 5 survived. The bodies of two of the victims were never recovered. One of the two flight attendants and the captain of the flight died in the crash. One of the crash victims was Beulah Zachary, the executive producer of the television series Kukla, Fran and Ollie, which was broadcast from 1947 to 1957. Also aboard the plane was Robert Emerson, a research professor at the University of Illinois who was internationally known for his research into plant photosynthesis, and Herbert Greenwald, a Chicago real estate developer.

The captain of the flight, Albert Hunt DeWitt, was 59 years old. He started his aviation career at in 1929 by flying for the Thompson Aeronautical Corporation of Cleveland, which was later acquired by American Airlines. A resident of Decatur, Michigan, he was qualified to fly all of the aircraft that had been operated by American Airlines and was considered one of the most experienced commercial pilots in the world, with seven million miles flown. He had a total of 28,135 hours of flight experience, including 48 hours in the Lockheed Electra and 2,500 hours of instrument time, and had at one time acted as one of American's chief pilots in the New York area. He learned to fly airplanes when he was 24 years old. In 1930, he had been involved in an accident while he was flying a mail plane over Mishawaka, Indiana, on his way to Chicago. Caught in a severe snowstorm, his aircraft stalled and entered a spin, but he was able to jump out of his plane before it crashed and he landed in a 75-foot-high tree. Before joining American Airlines, he had been a barnstormer in Indiana and Michigan and had been an instructor for various flying schools and clubs in the 1920s. He served in both World Wars; in World War I, he was a motorcycle courier, and during World War II, he served as an instructor at flight schools in New York and Chicago. He had planned to retire that May, but did not survive the crash of Flight 320. His cause of death was listed as drowning, but the medical examiner stated that he had also suffered severe internal injuries that would probably have been fatal had he not drowned.

The first officer, 33-year-old Frank Hlavacek, was a resident of Wilmette, Illinois, and had been employed with the company for eight years. He had a total of 10,192 logged hours, of which 36 hours were in the Electra. He had been flying since he was 14 years old and had served with the United States Army Air Forces in World War II. Before joining American Airlines, he had owned his own air service based in La Jolla, California. After the crash, he helped two of the survivors reach the remnants of the plane's wing, where they were rescued. He suffered fractures to his jaw, pelvis, and both legs in the crash as well as internal injuries, but eventually recovered and returned to work at American Airlines.

The flight engineer, Warren Cook, was 36 years old and had been working for American Airlines for eleven years. He had a total of 8,700 flying hours, of which 81 were in the Electra. He served in the United States Army Air Corps from 1940 to 1945. In the accident, he suffered a badly wrenched back, cuts, and bruises. After recovering from his injuries, he returned to work at American Airlines.

Crash investigation
Within two hours of the crash, investigators interviewed flight engineer Warren Cook. He told them he had felt that the flight's approach to the airport was completely routine and when the aircraft hit the water it was completely unexpected. The investigators had to wait to talk to first officer Frank Hlavacek because of his injuries, but several days later he told them that he had been calling out altimeter readings to Captain DeWitt during the descent in 100 ft increments as they approached the runway. He said that he had barely gotten the words out for 500 ft when the plane struck the river. Even though both pilots were interviewed at different times and at different locations, both pilots stated that the aircraft struck the river just as Hlavacek was saying "five hundred feet".

As soon as weather conditions allowed, investigators began the process of recovering the aircraft wreckage. They recovered 25 percent of the plane by February 5, and 50 percent by the next day. On the day after the crash, crews attempted to use salvage cranes to raise the fuselage of the aircraft out of the river, but they were only briefly successful before the wreckage broke apart and most of it fell back into the water. The tail section was recovered on the evening of February 5, and newspapers reported that the damage to that section hinted that the aircraft may have crashed in a "nose up" position, as though the pilots had noticed at the last minute that they were well short of the runway and tried to climb. Divers were deployed to locate missing sections of the aircraft beneath the surface of the water, but the efforts were hindered by high winds, strong river currents, and low visibility in the water. Some pieces of the plane had been swept away by currents and were found as far away as Northport, Long Island, more than 30 mi away. Each piece of the aircraft that was recovered was identified, tagged, cleaned off, and moved to Hangar 9 of the Marine Air Terminal of LaGuardia Airport. The nose section and cockpit of the plane were recovered late on February 7. The cockpit was in relatively good condition; the spring-wound clock on the instrument panel still working when the section was recovered from the river.

In response to the accident, on February 9, the FAA increased the minimum visibility requirements for Lockheed Electra landings during poor weather conditions. American Airlines and Eastern Airlines, the two airlines that were flying the Electras at that point, described the restrictions as temporary, likely lasting only a few days. Representatives of Lockheed Aircraft Corporation expressed disappointment in the new changes, but said the company would continue to cooperate with the investigation any way it could. The following day, the Agency reversed course, and said that the two airlines flying the Electra could resume flying with the previous visibility requirements.

Altimeter concerns
The altimeters used in the aircraft were an early focus of the investigation. The models that Lockheed had used in its Electra turboprops were a different style than what had been used in older piston-type aircraft. The older style used three hands of different lengths to indicate the aircraft's altitude, but the new design combined a single needle with graduations indicating hundreds of feet, and a rectangular display with numbers printed on a rotating drum that indicated thousands of feet. The Kollsman Instrument Corporation, which built both types, described the new style as a "precision drum altimeter" and said that it had been "developed as a result of a human engineering study made by the Aero Medical Laboratory, by an unnamed government body, and at the instigation of the Air Force, primarily to meet the needs of faster flying." The Air Force had reported multiple cases where its pilots had misread the older-style altimeters and had misinterpreted their altitude by 10,000 feet. On the other hand, pilots training on aircraft with the new-style altimeters reported several instances where they had misread the altitude, causing them to misinterpret the aircraft's altitude by up to 1,000 feet. Because of the confusion, early reports emerged that American Airlines had made plans to install an additional third, three-needle altimeter in the center of the instrument panel while continuing to use the newer style altimeters. Pilots for Eastern Airlines who had been flying the Electra aircraft also complained about the new style of altimeter, stating that not only were they easy to misinterpret, but they tended to be slower to show changes of altitude than the older style. That airline had installed a third, old-style, altimeter in their cockpits. American Airlines defended the new style altimeter as "a new and far superior altimeter with finer gradations" and denied that it had received complaints with the instruments. It acknowledged that it had planned to install a third altimeter in the center of the cockpits, but told the New York Times that the third unit was going to be a new-style model. At the same time, flight crews told the Chicago Tribune that the third unit was going to be an old-style altimeter. At the time of the accident, the aircraft in Flight 320 still only had the two new-style altimeters.

When the FAA reverse course about the more restrictive landing regulations for Electra aircraft, it did so on the condition that any new-style altimeters in the aircraft were replaced with old-style three-hand altimeters. Both Eastern and American agreed to immediately replace the altimeters as a precautionary step. On February 20, 1959, the FAA extended the restrictions to cover Boeing 707 aircraft that had been equipped with the new-style altimeters, citing unspecified "operational difficulties in the last few days".

The CAB held an investigative hearing in New York City beginning on March 18, 1959. In testimony before the board, first officer Hlavacek repeated the information that he had given in his earlier interviews, testifying that he and the other crew members had compared their altimeters several times during the flight, including when they passed Newark, New Jersey. He said that his altimeter and the captain's altimeter were very close. He said that at the time of the crash, the captain had primarily been using the automatic pilot with small manual adjustments during the approach. He also said that some ice had formed at the top of the windshield, but the flight crew did not consider it to be a safety hazard. He said that he had not seen any sign of the runway lights ahead, but that he had caught sight of a few reddish lights flashing past his side windows just before impact.

The investigative board confronted flight engineer Cook with details of an interview that he had given immediately after the accident. During the interview, he had said that the aircraft's altimeter had shown an altitude of less than one hundred feet at the time of impact. Cook responded that it showed five hundred feet, and at the time he had given the interview, he had been in a state of shock and that in his mind he had mistaken the one on the drum to mean one hundred feet instead of one thousand feet. He confirmed that he had turned on de-icing equipment before the plane had started its descent, and that the captain had been using the automatic pilot to fly the plane during the descent. He said that he had been flying with Captain Dewitt since 1951, that he knew him well, and that it was Dewitt's practice to use the automatic pilot to descend until about 400 feet above the ground, at which point he would switch to full manual control. He also testified that he had not seen the airport approach lights through the windshield, seeing nothing but blackness up to the time of the crash.

Accident investigators had taken the altimeters that were recovered from the crash to the instrument shop at La Guardia Airport for a detailed examination. On February 26, an article in the Chicago Tribune reported that after the altimeters had been cleaned of corrosion, water, and dirt, they were tested in a pressure chamber. According to the article, both of the devices functioned normally down to 1,000 feet above ground pressure level, but below 1,000 feet they stuck or lagged considerably. However, in testimony before the board during the March hearings, the manufacturer of the altimeters submitted written testimony that the instruments did not have any mechanical failure or malfunction before the crash. When they had been salvaged from the water, the pilot's and co-pilot's instruments had indicated minus 1,500 feet and minus 1,640 feet respectively, reflecting damage to parts of the instruments caused by immersion pressure. When questioned, the investigator acknowledged that there was no way to state exactly what the altimeters showed at the time of impact. In testimony before the CAB, American Airlines's director of flying said that a simultaneous malfunction of two altimeters at the same time was "almost mathematically impossible". The CAB heard from experts from the Lockheed Aircraft Corporation who had attempted to reproduce a 500-foot error in the reported altitude by simulating a buildup of ice in the air pressure lines that provide the input data to the altimeters. They flew an Electra plane behind an Air Force tanker that was spraying ice water to see if they could cause the pressure line to clog. In other tests, they intentionally plugged the line, used different methods of disrupting airflow into the port, and even had a mechanic spray a stream of water directly into the pressure port. None of the tests produced the 500-foot error that was reported by the pilots, and produced a maximum error of only of 40 or 50 feet.

In an attempt to discover why the crew of the Electra had not seen the runway ahead of them, the CAB heard from two pilots of a Northeast Airlines DC-3 that had landed at La Guardia Airport a minute or two ahead of the Electra. They testified that they had had no problem coming in under the 400-foot cloud ceiling and that they could see the whole mile-long runway ahead of them. However, crash survivors and sailors aboard the rescue tug stated that at the time of the crash, an isolated patch of fog and low clouds had moved over the river.

Final report
The CAB released a final report on the accident on January 10, 1960. The investigation concluded that the crew had been preoccupied with aspects of the flight and had failed to monitor essential flight instruments during the descent, leading to their descending below their intended glide path. Contributing to the accident were factors that included the crew's limited experience with the aircraft type, an unsafe approach technique where the autopilot was used to or almost to ground level, an incorrect setting of one of altimeters, and a possible misinterpretation of the altimeter and the rate of descent indicators on the aircraft. It also mentioned the poor weather conditions in the approach area and lack of visual references, causing the crew to misinterpret their height and altitude. The board was critical of the airline's lack of a comprehensive simulator training program for its pilots flying the Electra, calling the accident potentially avoidable if such a program had been in place. It also called for new regulations by the FAA to require that the installation of a flight data recorder in all large turbine-engine aircraft used in air transportation.

Investigators recovered over 90 percent of the primary structural components of the aircraft and most of the system's components. They found that at the moment of impact, the flaps were correctly set for the approach and that the landing gear was extended. The propeller blade angles were relatively uniform and consistent with the power readings displayed on the instruments recovered from the aircraft, and matched the power levels that the pilots said they were using during the approach. Neither of the two vertical speed indicator mechanisms were recovered. Both altimeters were recovered, but since the diaphragms of both had been overstressed due to submersion, it was impossible to determine if either of the altimeters had been displaying accurate information before the crash.

Investigators obtained all of the maintenance and pilot complaint records of all operators, civil and military, of the type of altimeter used in the flight. They did not find any incident that involved the failure of more than one of the altimeters at a time, and after reviewing the possibility of a simultaneous failure of both altimeters, the CAB concluded that it would involve such an extreme mathematical improbability that it chose to reject the theory of a simultaneous failure, and it rejected parts of the testimony of the surviving crew members. It concluded that after consideration of all possible scenarios, a failure of just one of the altimeters was also unlikely to have occurred. Based on eyewitness testimony and the analysis of the impact, the CAB concluded that it was likely that one or more of the pilots had misread the altimeter due to their unfamiliarity with the new style. It also said there was a possibility that in addition, the pilots had misread the vertical speed indicators, which used a different scale than what had been used in older aircraft and well as the in training that the captain had received.

The CAB concluded that all of the required airport, boundary, and runway lights were on and functioning at the time of the accident. However, because the lights were slanted upward at between three and five degrees, and because of a dike located between the end of runway 22 and the water, the CAB concluded that they would not have been visible to the crew because of the aircraft's premature descent below the cloud level.

The CAB's conclusions were soundly criticized by the president of the Air Line Pilots Association, who called the report "grossly inaccurate in a number of respects". He said the report failed to reasonably explain the cause of the accident, and it assumed factors that had not been established by fact. He said that all of the pilots at American Airlines were united in their criticism of the report, saying it "slandered and wrongfully accused" crew members of the plane, and was aimed at "conveniently writing the accident off the books" rather than accurately determining a cause. He said that in the association's judgement, the crash was the result of marginal weather conditions and inadequate approach and lighting aids at the airport. First officer Frank Hlavacek said he was "furious" over the CAB report, saying the board tried to take the easy way out by blaming a dead captain. He said he hoped that American Airlines would protest the report.

Additional investigations
On February 6, 1959, the United States House Commerce Committee named a special subcommittee to investigate the crash and the related safety issues that the aviation industry had been encountering during the transition from piston aircraft to jet and turboprop aircraft. The subcommittee was headed by Representative John Bell Williams of Mississippi, a former World War II bomber pilot. House Commerce Committee Chairman Oren Harris of Arkansas said the subcommittee would look at some aspects of the new aircraft, including the equipment that was being used and the training of the pilots. The seven members of the subcommittee visited LaGuardia Airport on February 12 and inspected the runway where Flight 320 had been approaching, but refused to publicly discuss the results of their investigation.

During hearings of the aviation subcommittee of the Senate Commerce Committee in January1960, the safety director for the CAB testified that if high intensity lights had been present at the LaGuardia runway, "the accident probably would not have happened". He also called for more training of copilots and for the installation of electronic flight recorders in aircraft to assist with accident investigations. As a result of the testimony, three of the senators on the subcommittee asked for the installation of modern lighting systems at Chicago's Midway Airport and other landing fields, and for new regulations that required copilots to be certified on the aircraft they fly. Elwood Richard Quesada, administrator of the FAA, testified that before the accident, the government had pledged to pay 75 percent of the cost to install high intensity lighting and radar approaches at La Guardia, but that officials at the airport had declined to pay the 25 percent that was required for local cooperation.

Legacy
Citing the lessons from the crash of American Airlines Flight 320, in March 1960, the FAA and the New York Port Authority announced plans to add approach lights and an instrument landing system to runway 22 at La Guardia Airport. Part of the project required the closure of the Rikers Island Channel and the construction of a replacement, requiring approval and coordination from the United States Army Corps of Engineers. The first phase, an 825 ft approach lighting system was completed in March 1961, extending just to the edge of the Rikers Island Channel. In 1962, the Port Authority announced that new approval for the relocation of the ship channel was expected, and that in addition to the instrument landing system, it would also extend runway 4/22 from 5000 ft to 7000 ft, and runway 13/31 from 5965 ft to 7000 ft. Runway 22 would be equipped with a full instrument landing system and a full 3000 ft approach lighting system. The $42 million project was completed in March 1966.

In 1957, the CAB started requiring the installation of a flight data recorder on all large turbine-powered aircraft that were used in civil aviation that were certified for flight above 25000 ft. Although the Lockheed Electra was able to fly higher than that, American Airlines elected to request certification of the Electra only to a maximum altitude of 25,000 feet, bypassing the requirement of flight data recorders. The final CAB Accident report, released in January 1960, made the recommendation that the FAA amend regulations to require the installation of flight data recorders in all large turbine-powered aircraft to provide a durable record that could assist air crash investigations. On April 1, 1960, The FAA announced that it would consider a rule to require the installation of flight recorders in all turbo-prop airliners. That July, it ordered the installation flight data recorders in turbine-powered carrier aircraft operated by U.S. Airlines by that November. The Air Transport Association complained that the minor improvement to crash investigatons was not worth the installation expense and extra weight of the recorders. The FAA did not back down, but it did extended the installation deadline to May 1, 1961. By 1964, the FAA proposed additional requirements for the installation of cockpit voice recorders in all large commercial aircraft by July 1966. Those recorders would assist air crash investigators by providing details about flight crew conversations during emergency situations.