One of the museums that we visited in D.C. was the National Air and Space Museum. To me, this was also the most exciting one. Like with all the other museums, the entry was free and we spent quite some time to go through all their different exhibits.
The aircrafts that they had available included passenger planes, fighters and a couple of drones as well.
A good portion of the museum was dedicated to space exploration and included Apollo Lunar and Command Modules, different rovers, satellites and rockets.
Quite a bit of russian space vehicles such as a Soyuz, some rockets and the actual spacecraft from the Apollo–Soyuz Test Project were shown in the museum as well.