Production of the 727 extended from the early 1960s to August 1984 -- a remarkable length of time, considering the original market forecast was for 250 airplanes. As it turned out, 1,831 were delivered. Twenty years later, when the last 727 was delivered, this versatile fleet was carrying 13 million passengers each month. As of January 2001, nearly 1,300 of the reliable aircraft were still in service.

On Jan. 13, 1991, the first 727 built -- which had been in continual service with United Airlines since 1964 -- finally made its last commercial flight and was donated to the Museum of Flight in Seattle.

Introduced into service in February 1964, the 727 trijet became an immediate hit with flight crews and passengers alike. With a fuselage width the same as the 707 (and the later 737 and 757), it provided jet luxury on shorter routes. With sophisticated, triple-slotted trailing edge flaps and new leading-edge slats, the 727 had unprecedented low-speed landing and takeoff performance for a commercial jet and could be accommodated by smaller airports than the 707 required.

The 727, like all Boeing jetliners, was continually modified to fit the changing market. It began with the -100 series, of which 407 were sold. This was followed by the -100C convertible that featured a main-deck side cargo door, allowing it to carry either cargo pallets or passengers -- or a combination of both -- on the main deck. Boeing built 164 of these.

The 727-200, introduced in December 1967, had increased gross weight and a 20-foot longer fuselage that could accommodate as many as 189 passengers in an all-tourist configuration. In all its variations, 1,245 of the -200s were sold. The last version, the 727-200F, had a 58,000-pound, 11-pallet cargo capability. Fifteen of these were sold to Federal Express.

Structural improvements, a more powerful engine and greater fuel capacity led to the Advanced 727-200 in May 1971. This advanced series had improved payload/range capability, better runway performance and a completely restyled "wide-body look" as standard equipment.

Lufthansa German Airlines and Air Algerie put 727s with the new interior into service in April 1971. Passenger response was enthusiastic, and by November 1972, this spacious interior was standard equipment on all production 707, 727 and 737 aircraft, and was offered for retrofit as well.

Later performance improvements for the 727 included another gross weight boost, from a maximum 170,000 pounds (77,122 kg) to 191,000 pounds (86,600 kg) for the Advanced version. On February 3, 1972, another increase to 208,000 pounds (94,348 kg) was announced, together with the purchase of three of the "heavyweights" by Sterling Airways of Denmark. The 727's highest gross weight was eventually raised to 210,000 pounds (95,300 kg).

The 727 became the best-selling airliner in history when orders passed the 1,000 mark in September 1972. By January 1983, orders reached 1,831. One Boeing-owned test airplane brought the grand total to 1,832. Today, the Boeing 737 has surpassed that total, but the 727 holds a permanent place in the annals of aviation as one of the most significant airplanes in the development of the world's jet transportation system.

On Dec. 5, 1977, the worldwide 727 fleet carried its one billionth (1,000,000,000) passenger -- a mark never attained before by a commercial aircraft. Today, the number has reached well over 4 billion.