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 Commercial Airplanes 61, would step down immediately and be replaced. Kevin G. McAllister was named president and CEO of Boeing Commercial Airplanes (BCA). For all models sold beginning with the Boeing 707 in 1957, except the 720, Boeing's naming system for commercial airliners has taken the form of 7X7 (X representing a number). All model designations from 707 through 787 have been assigned, leaving 797 as the only 7X7 model name not assigned to a product. For model numbers in the 707 to 777 range, the model number consists of an airplane's model number, for example 707 or 747, followed by a