One of the more remarkable warplanes of the last century is still in service. The U.S. B-52 bomber first flew in early 1952. It entered production two years later and eight different models were produced until production stopped in the late 1960s. Out of the 744 B-52s built, nearly a 100 H models remain in service. At the moment, the air force plans to keep these aircraft flying until 2040. Originally designed to drop nuclear weapons on the Soviet Union, the B-52 instead showed itself to be a remarkably effective heavy bomber during the Vietnam war. A B-52 weighs nearly 200 tons and has a 185 foot wingspan. The current version has a small crew, five or six depending on the mission. Normally it flies high (as far up as 50,000 feet), but was also designed to come in on the deck (as low as 200 feet.).