April 13,2008: After more than half a century of service, the U.S. Air Force has retired that the last of its twin jet T-37B training aircraft. The replacement is a single engine prop driven aircraft, the T-6A.

One of the most successful aircraft designs of the post-World War II era, the Cessna T-37 is a two engine primary jet trainer with a top speed of only about 680 kilometers an hour. Designed in1953, the T-37, affectionately nicknamed the "Tweet," entered service with the Air Force in 1957. Over the next eight years. 1,268 T-37s were produced in several models, including a ground attack version, the A-37, which has a much higher speed (830 kilometers an hour) and somewhat different overall characteristics. Most T/A-37s were still flying at the end of the Cold War. But since then, they have been retired at a rapid rate.

The versatile T-37 proved an attractive investment for nations wishing to stretch their defense dollars, and was procured for use by the U.S. and 14 other countries. The oldest T-37s have logged over 20,000 hours of light time, with the average well over 12,000 hours.

By 1996, all USAF T-37Bs completed a SLEP refit, extending their total useful life to over 30,000 hours. Regarded as a "user friendly" aircraft, by now the T-37Bs are basically worn out. The T-6A was selected as its replacement because this aircraft, based on the very popular Pilatus PC-9, already had an excellent reputation as a trainer aircraft.