A program to improve performance by using turbosupercharged engines was begun in November 1943 with plans for a P-61C production model, preceded by two XP-61C prototypes prepared by Goodyear, an important Northrop sub-contractor. A P-61A-5 and an A-10 were flown to Akron in May 1944 for modification and, after a engine model change from the planned R-2800-77 altered their designation to XP-61D, flight tests began with 2,800 hp R-2800-57 Wasps and CH-5 turbos in November 1944.
The first P-61C-1 with R-2800-73s was accepted on July 14, 1945, just before V-J Day curtailed production, and only 41 were delivered, the last on January 28, 1946. Top speed had increased from 366 to 430 mph and speed brakes on the wings could prevent the P-61C from overshooting targets, but this model was too late for combat. NORTHROP P-61B-15
The XP-61E was a long-range day fighter with radar and turret removed to provide a smaller, more streamlined fuselage. Two crewmen sat under a bubble canopy ahead of a fuselage fuel tank, while four .50-caliber nose guns supplemented the usual four 20-mm belly guns. Converted from a P-61B-10 with R-2800-65 Wasps, the first prototype flew on January 3, 1945. A second prototype was wrecked in April, but the AAF had already decided on the P-82B Twin Mustang as its long-range fighter, and developed the Northrop as a photo-reconnaissance type.

XP-61D

XP-61E

XP-61D

XP-61E

XP-61D

XP-61D

XP-61E