IWM Duxford is the place for military buffs. It is situated on a former RAF base just south of Cambridge that was home to an American fighter squadron during World War II. The museum chronicles the development of miliary aviation and, fittingly, has an entire wing featuring American aircraft and dedicated to the American airmen who died in war. The runway is flanked by a number of military aircraft, and two lovingly restored B-17 bombers sit on the flight line, just as they did during the war.
Despite its name, the museum has civilian aircraft as well, including several jet airliners and a Concorde prototype which you can walk through. A retired Concorde has recently been donated to the museum and a special hangar is being built for it.
There's more than just planes here. The museum also has tanks, howitzers and other 20th-century military equipment on display in its Land Warfare Hall. There are also exhibits on the Normandy landings as well as Field Marshal Bernard Law Montgomery, aka "Monty."