The P-38H (Model 222-81-20) differed from earlier versions in being powered by 1425 hp Allison V-1710-89/91 engines. The P-38H was fitted with automatic oil radiator flaps in order to solve a chronic engine overheating problem and enable military power above 25,000 feet to be increased from 1150 to 1240 hp. An M-2C cannon took the place of the M-1, and the bomb capacity for each underwing rack was raised to 1600 pounds. In most other respects, this model was identical to the P-38G-10-LO.
The first of 226 P-38H-1-LOs went into service in May of 1943. The 375 P-38H-5-LOs were fitted with B-33 instead of B-13 turbosuperchargers which gave improved high-altitude performance.
Empty weight was 12,380 pounds, normal loaded wright was 19,500 pounds, and maximum loaded weight was 20,300 pounds. Maximum speed was 402 mph at 25,000 feet. An altitude of 20,000 feet could be attained in 6.5 minutes. Service ceiling was 40,000 feet. Normal range was 350 miles, and maximum range with external tanks was 2400 miles.
Serials of the P-38H production run were as follows:
42-13559 Lockheed P-38H-1-LO Lightning 42-66502/66726 Lockheed P-38H-1-LO Lightning 42-66727/67101 Lockheed P-38H-5-LO Lightning