The Cessna T-37 Tweet (designated Model 318 by Cessna is a small, economical twin-engine jet trainer-attack type aircraft which flew for decades as a primary trainer for the United States Air Force (USAF) and in the air forces of several other nations. The A-37 Dragonfly variant served in the light attack role during the Vietnam War and continues to serve in the air forces of several South American nations.

The T-37 served as the U.S. Air Force's primary pilot training vehicle for over 52 years after its first flight. After completing Primary in the Tweet, students moved on to other advanced Navy, Marine Corps or Allied trainers. 1,269 Cessna T-37s were built, with 419 still serving in the United States Air Force in 2006. Between 2001 and 31 July 2009 the USAF phased out the T-37 in favor of the T-6 Texan II.

The T-37A was delivered to the U.S. Air Force beginning in June 1956. The USAF began cadet training in the T-37A during 1957. The first T-37B was delivered in 1959. Instructors and students considered the T-37A a pleasant aircraft to fly. It handled well and was agile and responsive, though it was definitely not overpowered. It was capable of all traditional aerobatic maneuvers. Students intentionally placed the aircraft into a spin as part of their pilot training.

The Air Force made several attempts to replace the T-37, but it remained in service with the USAF until it was phased out in favor of the Beechcraft T-6A Texan II between 2001 and 2009. The T-6 is a turboprop aircraft with more power, better fuel efficiency and more modern avionics than the Tweet.
The final USAF student training sortie by a T-37B aircraft in the Air Education and Training Command (AETC) took place on 17 June 2009. The last USAF operator of the T-37B, the 80th Flying Training Wing (80 FTW), flew the sortie from its home station at Sheppard AFB, Texas. The last T-37B was officially retired from active USAF service on 31 July 2009.