We're from the West Coast and stopped by the museum with friends who live in the DC area. We spent several hours exploring the museum, took the guided tour, which I would recommend, and really enjoyed the few hours we passed here. We haven't been to the main museum near the Mall that is affiliated with this one but found this place to be one of the better airplane museums we've seen. The exhibits that likely bring the most crowds are the Discovery Space Shuttle, the Enola Gay, and the Lockheed Blackbird. The Discovery was really neat but several other favorites were lesser known planes such as the Airphibian (a plane with wings that detached to create a car), the Messerschmitt Komet with it's comical pygmy propeller, and the Aichi Seiran, a Japanese war plane designed to operate from a submarine.
We appreciated the free entry (though didn't appreciate the $15 parking fee...make sure to carpool or look into public transportation). Another option is to come after 4 pm when parking is free. Hours currently are 10 am to 5:30 pm everyday except Christmas (closed) so if you don't want a guided tour or to spend a ton of time here, you could probably be satisfied with seeing the museum in an hour and a half to save the parking fee.
We appreciated the large variety of exhibits available but did find ourselves wishing each exhibit had more space so we could better appreciate each one. We couldn't walk around each plane and found them to be displayed together in such tight space that some of the displays resembled just a jumble of wings, wheels, and airplane parts. I think we were in part expecting to find a more spacious layout, such as the Evergreen Air & Space Museum in Oregon. That being said, if you're in the area, it's worth a visit!
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