After introducing the 707 in October 1958, Pan Am wanted a jet 2½ times its size, to reduce its seat cost by 30% to democratize air travel. In 1965, Joe Sutter left the 737 development to design the 747, the first twin aisle airliner. In April 1966, Pan Am ordered 25 747-100 aircraft and in late 1966, Pratt & Whitney agreed to develop its JT9D, a high-bypass turbofan. On September 30, 1968, the first 747 was rolled out of the custom-built Everett Plant, the largest building in the world by volume. The first flight took place on February 9, 1969 and the 747 was certified in December of that year. It entered service with Pan Am on January 22, 1970; it was the first airplane dubbed a "Jumbo Jet". The 747 is a quadjet airliner, initially powered by JT9D turbofan engines, then GE CF6 and Rolls-Royce RB211 engines for the original variants. With a ten-abreast economy seating, it typically accommodates 366 passengers in three travel classes. It has a pronounced 37.5° wing sweep, allowing a Mach 0.85 (490 kn; 900 km/h) cruise speed, and its heavy weight is supported by four main landing gear legs with four-wheel bogies each. The partial double-deck aircraft was designed with a raised cockpit so it could be converted to a freighter airplane by installing a front cargo door, as it was initially thought that it would eventually be superseded by supersonic transports. For many more details, incluing the long list of variants, click here. Specifications below are for the 747-400. For other models see the above link.