This place is simply huge, with an amazing collection of aviation and space relics. An SR-71, the Enola Gay, Space Shuttle Discovery, Boeing's 367-80 (the prototype/predecessor to the 707), an Air France Concorde... just their ability to wedge everything in here is impressive. There is an interesting display of a number of piston and jet engines as well, some in cutaway views. The observation tower has a nice view of Dulles. Be warned that while the museum is free, parking is $15, and they'll probably get some more money out of you at the gift shop. I'm a sucker for a bookstore, and they have some obscure titles and topics.
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