Second the nomination, well worth the visit. Should mention it is on the property of the Washington Navy Yard, so not really as easy to get to as the museums on the mall. Really not walkable from the mall. Base access, or a visitors pass, required.
Complete airplane wise, pretty much what is in the pictures show, but many interesting displays, and models. Highlights for me were the Trieste submersible (Marianas Trench), and the Atomic displays, including a Little Boy (pretty rare) and the arming plugs from the Hiroshima strike. There is an annex building as well that is a 100 yards or so from the main museum but easy to miss, also worth the stop- cold war emphasis, good submarine displays, full scale Trident missile (big!), landing craft, more models, a few more atomic weapons, etc.
Budget 2 hours for your average visitor. Naval enthusiasts could stay much longer, significant others of enthusiasts, maybe not so much
