No history of the United States Armed Forces could be written without a hefty section on the Air Force. Its official museum—located in Dayton, Ohio—is now open in its entirety for online exploration. Check out the presidential airplane used by J.F.K. and Richard Nixon, decommissioned W.W. II aircraft, and the Apollo 15 command module, which orbited the moon. Alongside these and many other objects, short informational videos give background and include centuries-spanning historical footage. —J.V.