It is a good 30 minute drive out of washington dc but well worth the trip. The museum is free but being on the grounds of Dulles, they charge $15 parking fee and there is plenty of parking. An Imax theatre is inside with at least 5 different films showing a day. We arrived with 10 minutes before the start of the free tour which takes place every couple of hours and joined in. It took approximately 2.5 hours although advertised as 1.5 but we really enjoyed it. The space shuttle is explained, the blackbird and many of the exhibits by tour guides who give their time for free and are very informative. Lots of opportunity to ask questions and take pictures and they are happy with you dropping out and rejoining at any time. I do recommend the tour as some of the stories of visitors that have come that used to fly the planes is wonderful. The enola gay was one of my highlights as was the wright flyer. There is a good shop and access to food although only mcdonalds. Places to grab water on the way around as well as seats near most of the planes for those needing a rest. A bonus is that you can go and look over the area where they are restoring planes and can see the staff working on them.
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