TWA Flight 553

Trans World Airlines (TWA) Flight 553 was a McDonnell Douglas DC-9-15 jet airliner, registration N1063T, operated by Trans World Airlines on March 9, 1967 between Pittsburgh, Pennsylvania and Dayton, Ohio. While descending toward Dayton about 29 mi from the airport, the flight collided in midair with a Beechcraft Baron, a small, general-aviation airplane, near Urbana, Ohio. All 25 aboard the DC-9 and the sole occupant of the Beechcraft were killed.

Summary
Flight 553 departed from Greater Pittsburgh International Airport en route to Dayton Municipal Airport. After passing Columbus, Ohio, Flight 553 had been cleared to descend from flight level (FL) 200 (about 20000 ft above sea level) to 3000 ft. The flight was in uncontrolled airspace but under the control of Dayton radar approach, which advised the pilots of uncontrolled visual flight rules (VFR) traffic ahead and slightly to the right and one mile away, about 18 seconds before the collision. The crew acknowledged the traffic advisory. As the airliner descended through 4500 ft at a speed of 323 knots on a southwest heading, its front right side collided with the left side of a southbound Beechcraft Baron 55. Both aircraft fell in Concord Township, a rural area northwest of Urbana in Champaign County. The collision occurred just northeast of the intersection of Melody Lane and Woodville Pike.

Cause
Visual flight rules (VFR) were in effect at the time of the accident, meaning that the pilots of both aircraft were responsible to "see and avoid" each other. In addition, the radar controller stated that he did not see the Beechcraft on his radar scope until 22 seconds before the crash. Controllers testified that the zone near the crash site was one in which small planes could be difficult to detect on radar, but flight checks in the area proved inconclusive.

The National Transportation Safety Board investigated the accident and determined that because of the DC-9's high rate of descent, its pilots were not able to see the other plane in time to avoid a collision. Weather conditions included widely scattered, thin clouds, with haze reducing visibility to 6 to 7 mi, twice the 3 mi visibility required for VFR flight.

Aftermath
Enacted in 1961 in the wake of the 1960 New York mid-air collision, FAR Part 91.85 mandated speed restrictions below 10000 ft within 30 nautical miles of a destination airport. After the accident involving Flight 553, all areas below 10000 ft were prohibited from exceeding 250 kn IAS. The accident also influenced the Federal Aviation Administration's decision to create terminal control areas or TCAs (now called Class B airspace) around the busiest airports in the country. The airspace around Dayton did not become a TCA, undergoing only minor changes until it was reclassified as Class C airspace in the late 1980s.