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The Boeing 747 is a wide-body commercial jet airliner and cargo aircraft, often referred to by its original nickname, Jumbo Jet, or Queen of the Skies. Its distinctive "hump" upper deck along the forward part of the aircraft makes it among the world's most recognizable aircraft,[1] and it was the first wide-body produced. Manufactured by Boeing's Commercial Airplane unit in the United States, the original version of the 747 had two and a half times greater capacity than the Boeing 707,[2] one of the common large commercial aircraft of the 1960s. First flown commercially in 1970, the 747 held the passenger capacity record for 37 years.[3] The four-engine 747 uses a double deck configuration for part of its length. It is available in passenger, freighter and other versions. Boeing designed the 747's hump-like upper deck to serve as a first class lounge or extra seating, and to allow the aircraft to be easily converted to a cargo carrier by removing seats and installing a front cargo door. Boeing did so because the company expected supersonic airliners (development of which was announced in the early 1960s) to render the 747 and other subsonic airliners obsolete, while the demand for subsonic cargo aircraft would be robust well into the future.[4] The 747 was expected to become obsolete after 400 were sold,[5] but it exceeded critics' expectations with production passing the 1,000 mark in 1993.[6] By August 2015, 1,512 aircraft had been built, with 29 of the 747-8 variants remaining on order.[7] The 747-400, the most common passenger version in service, has a high-subsonic cruise speed of Mach 0.85–0.855 (up to 570 mph or 920 km/h) with an intercontinental range of 7,260 nautical miles (8,350 mi or 13,450 km).[8] The 747-400 passenger version can accommodate 416 passengers in a typical three-class layout, 524 passengers in a typical two-class layout, or 660 passengers in a high density one-class configuration.[9] The newest version of the aircraft, the 747-8, is in production and received certification in 2011. Deliveries of the 747-8F freighter version to launch customer Cargolux began in October 2011; deliveries of the 747-8I passenger version to Lufthansa began in May 2012. The 747 is to be replaced by the Boeing Y3 (part of the Boeing Yellowstone Project) in the future. Development Background In 1963, the United States Air Force started a series of study projects on a very large strategic transport aircraft. Although the C-141 Starlifter was being introduced, they believed that a much larger and more capable aircraft was needed, especially the capability to carry outsized cargo that would not fit in any existing aircraft. These studies led to initial requirements for the CX-Heavy Logistics System (CX-HLS) in March 1964 for an aircraft with a load capacity of 180,000 pounds (81,600 kg) and a speed of Mach 0.75 (500 mph or 805 km/h), and an unrefueled range of 5,000 nautical miles (9,260 km) with a payload of 115,000 pounds (52,200 kg). The payload bay had to be 17 feet (5.18 m) wide by 13.5 feet (4.11 m) high and 100 feet (30.5 m) long with access through doors at the front and rear.[10] Featuring only four engines, the design also required new engine designs with greatly increased power and better fuel economy. On May 18, 1964, airframe proposals arrived from Boeing, Douglas, General Dynamics, Lockheed and Martin Marietta; while engine proposals were submitted by General Electric, Curtiss-Wright, and Pratt & Whitney. After a downselect, Boeing, Douglas and Lockheed were given additional study contracts for the airframe, along with General Electric and Pratt & Whitney for the engines.[10] All three of the airframe proposals shared a number of features. As the CX-HLS needed to be able to be loaded from the front, a door had to be included where the cockpit usually was. All of the companies solved this problem by moving the cockpit above the cargo area; Douglas had a small "pod" just forward and above the wing, Lockheed used a long "spine" running the length of the aircraft with the wing spar passing through it, while Boeing blended the two, with a longer pod that ran from just behind the nose to just behind the wing.[11] In 1965 Lockheed's aircraft design and General Electric's engine design were selected for the new C-5 Galaxy transport, which was the largest military aircraft in the world at the time.[10] The nose door and raised cockpit concepts would be carried over to the design of the 747.[12] Airliner proposal The 747 was conceived while air travel was increasing in the 1960s.[13] The era of commercial jet transportation, led by the enormous popularity of the Boeing 707 and Douglas DC-8, had revolutionized long-distance travel.[13][14] Even before it lost the CX-HLS contract, Boeing was pressed by Juan Trippe, president of Pan American World Airways (Pan Am), one of their most important airline customers, to build a passenger aircraft more than twice the size of the 707. During this time, airport congestion, worsened by increasing numbers of passengers carried on relatively small aircraft, became a problem that Trippe thought could be addressed by a large new aircraft.[15] In 1965, Joe Sutter was transferred from Boeing's 737 development team to manage the design studies for a new airliner, already assigned the model number 747.[16] Sutter initiated a design study with Pan Am and other airlines, to better understand their requirements. At the time, it was widely thought that the 747 would eventually be superseded by supersonic transport aircraft.[17] Boeing responded by designing the 747 so that it could be adapted easily to carry freight and remain in production even if sales of the passenger version declined. In the freighter role, the clear need was to support the containerized shipping methodologies that were being widely introduced at about the same time. Standard containers are 8 ft (2.4 m) square at the front (slightly higher due to attachment points) and available in 20 and 40 ft (6.1 and 12 m) lengths. This meant that it would be possible to support a 2-wide 2-high stack of containers two or three ranks deep with a fuselage size similar to the earlier CX-HLS project. A view of an early-production 747 cockpit An Iran Air 747-200, showing the early-production 747 cockpit, located on the upper deck In April 1966, Pan Am ordered 25 747-100 aircraft for US$525 million. During the ceremonial 747 contract-signing banquet in Seattle on Boeing's 50th Anniversary, Juan Trippe predicted that the 747 would be "... a great weapon for peace, competing with intercontinental missiles for mankind's destiny".[18] As launch customer,[19][20] and because of its early involvement before placing a formal order, Pan Am was able to influence the design and development of the 747 to an extent unmatched by a single airline before or since.[21] Design effort Ultimately, the high-winged CX-HLS Boeing design was not used for the 747, although technologies developed for their bid had an influence.[22] The original design included a full-length double-deck fuselage with eight-across seating and two aisles on the lower deck and seven-across seating and two aisles on the upper deck.[23] However, concern over evacuation routes and limited cargo-carrying capability caused this idea to be scrapped in early 1966 in favor of a wider single deck design.[19] The cockpit was, therefore, placed on a shortened upper deck so that a freight-loading door could be included in the nose cone; this design feature produced the 747's distinctive "bulge".[24] In early models it was not clear what to do with the small space in the pod behind the cockpit, and this was initially specified as a "lounge" area with no permanent seating.[25] The Pratt & Whitney JT9D turbofan suspended under the wing pylon of the 747 prototype. It is stripped of its outer casing, revealing the engine's core at The Museum of Flight in Seattle, WA The Pratt & Whitney JT9D high-bypass turbofan engine was developed for the 747. One of the principal technologies that enabled an aircraft as large as the 747 to be conceived was the high-bypass turbofan engine.[26] The engine technology was thought to be capable of delivering double the power of the earlier turbojets while consuming a third less fuel. General Electric had pioneered the concept but was committed to developing the engine for the C-5 Galaxy and did not enter the commercial market until later.[27][28] Pratt & Whitney was also working on the same principle and, by late 1966, Boeing, Pan Am and Pratt & Whitney agreed to develop a new engine, designated the JT9D to power the 747.[28] The project was designed with a new methodology called fault tree analysis, which allowed the effects of a failure of a single part to be studied to determine its impact on other systems.[19] To address concerns about safety and flyability, the 747's design included structural redundancy, redundant hydraulic systems, quadruple main landing gear and dual control surfaces.[29] Additionally, some of the most advanced high-lift devices used in the industry were included in the new design, to allow it to operate from existing airports. These included slats running almost the entire length of the wing, as well as complex three-part slotted flaps along the trailing edge of the wing.[30] The wing's complex three-part flaps increase wing area by 21 percent and lift by 90 percent when fully deployed compared to their non-deployed configuration.[31] Boeing agreed to deliver the first 747 to Pan Am by the end of 1969. The delivery date left 28 months to design the aircraft, which was two-thirds of the normal time.[32] The schedule was so fast paced that the people who worked on it were given the nickname "The Incredibles".[33] Developing the aircraft was such a technical and financial challenge that management was said to have "bet the company" when it started the project.[19] Production plant