The P-51 was designed as the NA-73 in 1940 at Britain's request. The design showed promise, and AAF purchases of Allison-powered Mustangs began in 1941, primarily for photo recon and ground support use due to its limited high-altitude performance. But in 1942, tests of P-51s using the British Rolls-Royce "Merlin" engine revealed much improved speed and service ceiling, and in December 1943 Merlin-powered P-51Bs first entered combat over Europe. Providing high-altitude escort to B-17s and B-24s, they scored heavily over German interceptors, and by war's end, P-51s had destroyed 4,950 enemy aircraft in the air, more than any other fighter in Europe.

Mustangs served in nearly every combat zone, including the Pacific where they escorted B-29s to Japan from Iwo Jima. Between 1941 and 1945, the AAF ordered 14,855 Mustangs (including A-36A dive bomber and F-6 photo recon versions), of which 7,956 were P-51Ds. During the Korean War, P-51Ds were used primarily for close support of ground forces until withdrawn from combat in 1953.

The National Museum of the United States Air Force has a P-51D on display in its Air Power Gallery.

Type Number built/
converted Remarks
XP-51 2 Model NA-73; developed for UK
P-51 150 Prod. model; four 20mm cannon
P-51A 310 Fitted with bomb racks; four .50-cal. mgs.
XP-51B 2 (cv) Improved P-51; was XP-78
P-51B-NA 1,988 Prod. model; Blocks 1-15; Inglewood
P-51C-NT 1,750 Dallas plant; Blocks 1-11
P-51D-NA 6,502 Bubble canopy; Blocks 1-30
P-51D-NT 1,454 Blocks 5-30; six .50-cal. mgs.
TP-51D-NT 10 Two-place trainer variant
P-51E 0 Designation not assigned
XP-51F 3 Exp. lt. weight test model
XP-51G 2 Modified XP-51F with new engine
P-51H-NA 555 Prod. model; Blocks 1-10
XP-51J 2 Modified XP-51F with new engine
P-51K-NT 1,337 Improved D; Aeroprop; Blocks 1-15
P-51L-NA 1 Improved H with new engine
P-51M-NT 1 Improved H with new engine

Span: 37 ft. 0 in.
Length: 32 ft. 3 in.
Height: 13 ft. 8 in.
Weight: 12,100 lbs. maximum
Armament: Six .50-cal. machine guns and 10 5-in. rockets or 2,000 lbs. of bombs
Engine: Packard-built Rolls-Royce "Merlin" V-1650 of 1,695 hp
Cost: $54,000

Maximum speed: 437 mph
Cruising speed: 275 mph
Range: 1,000 miles
Service ceiling: 41,900 ft.