On April 4, 1973, the first Tiger II reached the 425th Tactical Fighter Training Squadron at Williams AFB, Arizona. This squadron was assigned the task of training the aircrews of nations that had acquired the F-5E under the Mutual Assistance Pact (MAP). Contrary to what some other sources have said, these F-5E/Fs carried USAF serial numbers and were procured through normal aircraft procurement procedures and channels.
Although the USAF never did adopt the F-5E as a front-line combat aircraft, it did adopt the F-5E as a specialized aircraft for dissimilar air combat training (DACT). Dedicated aggressor squadrons were formed in the wake of a precipitous and alarming decrease in the USAF's kill:loss ratio in combat in Southeast Asia. The US Navy's Top Gun program had turned around F-4 combat operations over Vietnam, and a similar program was proposed for the Air Force. A dedicated aggressor squadron (the 64th Fighter Weapons Squadron) was instituted during 1972 at Nellis AFB, with T-38s borrowed from Training Command as interim equipment. It was later joined by the 65th Fighter Weapons Squadron.
The T-38s were actually trainers and were not ideal in the role of simulating the performance of the MiG-21, but the choice was driven by expediency. Since the F-5E had approximately the size and performance characteristics of a MiG-21, it was deemed to be a better choice. It just so happened that a batch of F-5Es was available--having been originally destined for delivery to South Vietnam and now becoming suddenly available when the South collapsed. Beginning in 1975, some 70 F-5Es were turned over to the 64th and 65th Fighter Weapons Squadrons of the 57th TFW at Nellis AFB in Nevada. These aggressor squadrons were initially designated as Fighter Weapons Squadrons, then as Tactical Fighter Training Aggressor Squadron, and eventually simply as Aggressor Squadrons.
At the same time, F-5Es were allocated to two more units that were created overseas. the 527th Aggressor Squadron of the 10th TRW in the UK at RAF Alconbury and the 26th Aggressor Squadron, 3rd TFW in the Philippines at Clark AB.
The Clark-based 26th TFS remained in non-operational status until the end of August of 1975, by which time the 405th Fighter Wing had been replaced by the 3rd TFW at Clark. Even then, it did not start training activities until January 1976, using a number of T-38s made surplus by the arrival of the F-5Es at Nellis. Eventually, it received the F-5E, with some of the planes coming from an embargoed Ethiopian air force order. By that time it had been redesignated Tactical Fighter Training Squadron, and secondly as a Tactical Fighter Training and Aggressor Squadron. Eventually, it became just an Aggressor Squadron.
The RF-4C-equipped 10th Tactical Reconnaissance Wing at RAF Alconbury was chosen as the parent of the USAF in Europe's aggressor unit. This formed as the 527th Tactical Fighter Training and Aggressor Squadron in April of 1976 and was equipped with the F-5E in May. It began providing aggressor support to European-based combat units in September. It was subsequently renamed as the 527th Aggressor Squadron.
The Nellis-based units made frequent trips to various bases throughout the USA. The Alconbury aircraft regularly exercised with fighters from the RAF, Germany, and France, and established a near-permanent presence at Decimomannu on Sardinia.
The aggressor F-5Es were painted in a variety of colorful camouflage schemes designed to mimic those in use by Warsaw Pact aircraft. Two-digit Soviet-style nose codes were applied to most aggressor aircraft, and these coincided with the last two digits of the serial number. When there was duplication, three digits were used. International conventions made it necessary for military aircraft to carry their national insignia, but the star-and-bar national insignia was reduced in size and relocated to a less-conspicuous position on the rear fuselage. Aggressor units were among the first to apply the star and bar in toned-down or stencil form.
In the late 1980s, the fleet of aggressor F-5Es was getting rather worn out as a result of sustained exposure to the rigors of air combat maneuvering. The problem began with the loss of F-5F 73-0890 based at Williams AFB. It was lost in a training accident in which it broke in half during maneuvering, killing both the student and instructor pilot. An investigation later showed that the most likely cause of the accident was a failure in the upper fuselage longeron, probably a result of fatigue or corrosion. An inspection later showed that about a third of the fleet had cracked or fatigued upper longerons. Although no stateside aircraft were grounded (although some planes based at Clark AB and RAF Alconbury were grounded), they were restrictions placed on operations in which pilots were warned not to exceed a certain G-load. Some repair kits had to be devised to overcome these problems, and the estimated cost of repair of the entire fleet was beginning to exceed a billion dollars. In addition, the appearance of a new generation of Soviet fighters made it apparent that that F-5Es could no longer adequately mimic Warsaw Pact threats.
Consequently, the USAF began to consider retiring the F-5E/F fleet from service and started looking around for a successor. The F-16 was chosen as the successor, and F-16s began to be procured as F-5E/F replacements. However, since the F-16 was already in the USAF inventory, the dissimilar aspect of DACT was lost.
The 64th AS at Nellis ceased operations on April 1, 1988 in preparation to transitioning to the F-16. The 65th AS kept on flying the F-5E for another year or so to cover the transition period. The 65th AS F-5Es flew their last aggressor flight on April 7, 1989. The 527th AS flew its last F-5E sortie from Alconbury on June 22, 1988, transitioning to F-16Cs by mid January of 1989. The 26th AS at Clark was scheduled to dispose of its F-5Es in favor of F-16C/Ds and transfer to Kadena on Okinawa in early 1990.
However, in 1990, the decision was made to terminate the entire USAF aggressor program. The 527th AS was inactivated in late autumn of 1990. The 26th AS was disbanded before it could receive its new F-16s. The 64th and 65 AS were inactivated in 1990, but the loss of these two squadrons did not mark the complete termination of aggressor activities at Nellis. A small element formally known as the Adversary Tactics Division of the 57th Wing remains active at Nellis with a dozen or so camouflaged F-16Cs for the support of Red Flag exercises.
Many of the aggressor F-5Es were refurbished and delivered to foreign customers, but some were consigned to storage at Davis Monthan AFB in Arizona. Most of the rest were transferred to the Navy and the Marine Corps for use in their aggressor programs, initally going to three Navy squadrons and one Marine squadron. Contrary to the usual procedure, the Marines got first pick of the aircraft, choosing the planes with the lowest airframe times and carefully reviewing maintenance records. The norm at that time was for the Marines to receive hand-me-down aircraft from the Navy.