The Grumman F9F Panther was the manufacturer's first jet fighter and the US Navy's second. It first flew in 1947. Its power source was a Rolls-Royce Nene turbojet built under license by Pratt & Whitney as the J42. Since there was insufficient space within the wings and fuselage for fuel for the thirsty jet, permanently mounted wingtip fuel tanks were added. The F9F-2B version was fitted with underwing racks for bombs and rockets. All F9F-2's were eventually so modified, and the B designation was dropped.