The P-38F was first built from April 1942 and incorporated racks inboard of the engines for extra fuel tanks or 2,000lbs of bombs. The P-38F was heavier and with more powerful engines used more fuel so had a shorter range. A total of 527 P-38F were built. Following the P-38G which had more powerful engines than the F, the P-28H had yet more powerful Allison engines, an improved 20mm cannon and capacity for 3,000 of bombs.