The United States Air Force (USAF) was already using the straight-wing, jet-powered Cessna T-37 "Tweet" as its primary trainer by the time of its involvement in the Vietnam War (1955-1975). The aircraft were introduced in 1957 and managed a role into 2009 with some 1,269 being built. As the American commitment to the war grew, so too did its needs and among these was for a stable, light-class ground attack platform of which a pair of T-37C models were evaluated for the role. From this was born a revised version of the Tweet family line, given the designation of "A-37" and the nickname of "Dragonfly" and over 600 of the type were eventually built/modified under the Cessna brand label. These went on to see service with the USAF, South Vietnamese forces, Chile and Peru among others.
Compared to the T-37, the A-37 was given several notable modifications for the light attack role. Its undercarriage and wings were reinforced and wingtip fuel tanks were increased in size to promote better loitering times and operational ranges. The fuselage also accepted an internal General Electric Minigun Gatling system for close-range strafing. The cockpit was updated to include modern USAF weapons support, navigation and communications equipment. Each wing was initially granted use of three hardpoints and cleared to carry various types of USAF ordnance in inventory. The crew of two remained from the original Tweet and were seated in a side-by-side arrangement complete with the original's dual control scheme. Vision was largely good thanks to the lightly-framed canopy. The aircraft was powered by 2 x General Electric J85-J2/5 turbojet engines with approximately 2,400lb of thrust output each.
From this revision was born the "YAT-37D" prototype used to prove the platform viable to USAF authorities. First flight was recorded in October of 1964 and, after a period of growing disinterest in the type which delayed service entry, mounting losses of other close-support systems forced USAF attention back onto the A-37 project. A second prototype was added during testing and this model included an additionally pair of weapons pylons for greater munitions support. The YAT-37D then graduated from its testing role into the "AT-37D" which then evolved to the finalized "A-37A" designation and subsequent production models.
As completed, the A-37 was given a wide, squat forward fuselage which tapered rather nicely to the rear. The wings were straight in their design and capped by wingtip fuel tanks. Underwing pylons were held well outboard of the fuselage. The twin engine arrangement, buried in the fuselage, was aspirated by a pair of small intakes to either side of the aircraft. The empennage included a single vertical tail fin with mid-set horizontal planes. The undercarriage was wholly retractable and short, leading to the aircraft having a very low profile when at rest.
Thirty-nine conversions of T-37 aircraft made up the initial A-37A production models. These were then followed the definitive 577 "A-37B" model with its uprated General Electric J85-GE-17A turbojet engines of 2,850lbs thrust each. These aircraft also featured in-flight refueling capabilities as well as improved internal fuel stores to help offset the aircraft's inherent limited range. The airframe was further reinforced for the rigors of low-altitude flight and attack. The final Dragonfly variant to appear was the reconnaissance-minded OA-37B, born of the A-37B models, and serving in the armed reconnaissance role.
Over two dozen A-37As were delivered to Southeast Asia in August of 1967 for active evaluations in the theater by the USAF. These served primarily in the Close-Air Support (CAS) role, Forward Air Control (FAC), night attack, armed escort and armed reconnaissance roles. With a healthy stable of munition options, the little Dragonfly proved of great value as it could strafe targets with machine gun and cannon fire, drop conventional ordnance and fire unguided rockets via pods. While none were lost in the early-going, this period served to showcase some limitations of the system - namely in its operational reach. It was this that pushed a longer-endurance model that became the A-37B which arrived in prototype form during September 1967. Unlike the previously converted A-37A models, A-37B platforms were all "new-build" airframes from Cessna. Before the end of the Vietnam War, American A-37s were passed on to the South Vietnamese Air Force which, in turn, led them to be captured by the victorious North after the American withdrawal.
Beyond the Vietnam Conflict, other notable combat actions involving the A-37 was recorded during the Salvadoran Civil War where A-37Bs, delivered from U.S. stocks, were operated by the Salvadoran Air Force against rebels.
In all, operators of the A-37 proved plenty and many were delivered to customers across Central and South America - Colombia, Chile, Ecuador, El Salvador, Guatemala, Honduras, Peru and Uruguay. Southeast Asian operators included South Korea, South Vietnam, Thailand and Vietnam proper (captured specimens). Many A-37s exist as museum showpieces today while, rather amazingly, some 50 still operate in a frontline role (mainly across Central/South America).
Performance specifications included (A-37B) a maximum speed of 505 miles per hour, a cruising speed near 490 miles per hour and a ferry range out to 920 miles. Its combat radius equaled 460 miles while the aircraft could reach altitudes of nearly 42,000 feet. Rate-of-climb was approximately 7,000 feet per minute.
American Vietnam-era pilots affectionately referred to their Dragonflies as "Super Tweets" in honor of their origin.