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 CFM56, and is 40 dB quieter than JT3D engines that are being replaced. The first commercial orders for the 707 came on October 13, 1955, when Pan Am committed to 20 707s and 25 Douglas DC-8s, dramatically increasing their passenger capacity (in available revenue passenger seat-miles per hour/per day) over its existing fleet of propeller aircraft. The competition between the 707 and Douglas DC-8 was fierce. Pan American ordered these planes, when and as they did, so that they would be the operators of the "first-off" production line for each aircraft type. Until their initial batch of the aircraft had