aircraft Foreign aircraft have been used as aggressors in the United States, most notably the Israeli Kfir fighter, designated F-21 in its use as an adversary asset. Actual Soviet MiG-17s, 21s, and 23s have also been flown by the US Air Force as Aggressors over the Nellis ranges, under the Constant Peg program. The US Army operates eleven Soviet or Russian aircraft for adversary training, including Mi-24 Hinds, Mi-8 Hips, Mi-2 Hoplites, and An-2 Colts. German MiG-29 aircraft were regular visitors to the United States before being sold to Poland and participated in valuable DACT training at Nellis AFB as well as NAS Key West in addition to providing details to overseas locations or hosting US squadrons in Germany. One MiG-29 was loaned to the US for evaluation providing insight in the threat technology. The Navy and Marine Corps briefly operated 2 squadrons of F-21 Kfir Adversaries at NAS Oceana (VF-43) and Marine Corps Air Station Yuma (VMFT-401). Aggressor performances While aircraft used for the aggressor role are usually older jet fighters, this has not always been the case. During the mid-1980s, the US Navy determined that the A-4s and F-5s flown at Top Gun were not adequate in simulating the air-to-air capabilities of the newest Soviet fighters such as the MiG-29 and Su-27. At this point, the U.S. Navy held a competition for an adversary platform that could viably represent fourth-generation fighter threats embodied by the MiG-29, Su-27 and the Mirage 2000. The competing airframes were the General Dynamics F-16C Falcon and the Northrop F-20 Tigershark. According to George Hall's "Top Gun", many instructors at the Navy Fighter Weapons School preferred that the Navy procure the F-20. One reason given was the similarity to the F-5E Tiger aircraft already used by Top Gun and the four active duty adversary squadrons (VF-43, VF-45, VF-126, and VFA-127). However, General Dynamics priced the Falcon for the Navy at below cost. The F-16C won the competition and the F-20 failed to win another order. This, compounded with other lost contracts, led to the demise of the F-20 program and the elimination of one more competitor for the F-16 in the worldwide fighter market. The F-16C as procured by the Navy was equipped with the lighter AN/APG-63 radar set as flown in the F-16A and had a titanium wing spar as in other F-16s. It was not equipped with the M61 Vulcan gun system