P-51 Mustangs lasted in service far longer than one would initially think.

The last U.S. military use of the F-51 was in 1968, when the U. S. Army employed a vintage F-51D (44-72990) as a chase aircraft for the Lockheed YAH-56 Cheyenne armed helicopter project. This aircraft was so successful that the Army ordered two F-51Ds from Cavalier (the civilian company that had purchased the rights to the plane) in 1968 for use at Fort Rucker as chase planes. They were assigned the serials 68-15795 and 68-15796. These F-51s had wingtip fuel tanks and were unarmed. Following the end of the Cheyenne program, these two chase aircraft were used for other projects. One of them (68-15795) was fitted with a 106 mm recoilless rifle for evaluation of the weapon's value in attacking fortified ground targets.  Cavalier Mustang 68-15796 survives at the Air Force Armament Museum, Eglin AFB, Florida, displayed indoors in World War II markings.

The El Salvador Air Force purchased five Cavalier Mustang IIs (and one dual control Cavalier TF-51) that featured wingtip fuel tanks to increase combat range and up-rated Merlin engines. Seven P-51D Mustangs were also in service.  They were used during the 1969 Soccer War against Honduras, the last time the P-51 was used in combat. One of them, FAS-404, was shot down by a F4U-5 flown by Cap. Fernando Soto in the last aerial combat between piston engine fighters in the world.

The last time Mustangs were deployed for military purposes was a shipment of six Cavalier II Mustangs (without tip tanks) delivered to Indonesia in 1972–1973, which were replaced in 1976.

The Dominican Republic (FAD) was the largest Latin American air force to employ the P-51D, with six aircraft acquired in 1948, 44 ex-Swedish F-51Ds purchased in 1948 and a further Mustang obtained from an unknown source.  It was the last nation to have any Mustangs in service, with some remaining in use as late as 1984. Nine of the final 10 aircraft were sold back to American collectors in 1988.