IRON QUAD P-51 Mustang 450mm RTFThe P 51 Mustang is an American long range, single seat fighter, and fighter bomber used during WWII and the Korean War by the U. S. Army Air Forces. The D variant was upgraded to the Packard V 1650 7 engines and added (2) . 50cal AN M2 machine guns with a total of 6. The D variant became the most widely produced and became popular civilian warbirds and air racing aircrafts after its service in the U. S. military.