Boeing 707 ushering in the Jet Age. It established Boeing as one of the largest manufacturers of passenger aircraft, and led to the later series of airliners with "7x7" designations. The later 720, 727, 737, and 757 share elements of the 707's fuselage design. The 707 was developed from the Boeing 367-80, a prototype jet first flown in 1954. A larger fuselage cross-section and other modifications resulted in the initial-production 707-120, powered by Pratt & Whitney JT3C turbojet engines, which first flew on December 20, 1957. Pan American World Airways began regular 707 service on October 26, 1958. Later derivatives included the
Boeing 707 longer than the 707-320B and would have carried 209 passengers in mixed-class configuration and 260 passengers in all-economy configuration. The 506 model would have had a fuselage longer than the 707-320B and would have carried 225 passengers in mixed class configuration and 279 passengers in all economy configuration. Like the 707-620, the 707-820 was also set to compete with the stretched DC-8s. The design was being pitched to American, TWA, BOAC, and Pan Am at the time of its proposal in early 1965. The 707-820 would have cost US$10,000,000. Like the 707-620, the 707-820 would have required a massive structural