>But it may be worth pointing out that this annex to the Smithsonian Air and Space Museum is out by Dulles and not very convenient for visitors to access.

It's also the better campus IMO. The one in DC is basically a speed run of the stuff you see in a kids book that just highlights all the "firsts". The one at Dulles has all the cool displays of big or technologically unique stuff.

I agree access isn't great if you're trying to shoehorn it into a visit to all the typical DC monuments type stuff.