The North American P-51 Mustang was used in WWII on the Allied side. It was mainly used as an aomber escort over Germany, but also in the Pacific War. Because of these escorts, they were designed to travel very far. The P-51 became the USAF's flagship fighter in World War II.
Most of the P-51's wartime escorts were over Germany defending the B-17s from attack. It also saw combat in the Pacific War against Japan. The P-51 was used in the Korean War as well. It was one of the last propellar fighters to be used, being replaced by jets in later years.
Although more expensive to build, the P-51 was very durable and though to take down. The Japanese in World War II had trouble matching this plane, and instead built their planes to be built quickly in order to swarm the enemy. This tatic worked as long as the pilots didn't panic.
World War II
At a conferance during World War II, the Allies developed a plan to bomb Germany around the clock. The RAF would bomb by night, and the USAF by day. The USAF needed fighters to defend their bombers against enemy fighter planes. The P-51 Mustang was their answer.