Air museums? Pah
Go to the Udvar-Hazy center by IAD airport (Washington DC/Northern Virginia).
1. It's free (parking is ~$15, but there is a free shuttle bus from the airport, which takes about 15 minutes)
2. It has an SR-71A. Ooh!
3. It has a space shuttle. Aah!
4. It has the Enola Gay. OK, you had me at #1.
And to think, this is the *extension* museum. Downtown in DC proper they have an embarrassment of riches: the Apollo 11 module, Russian SS-20 missiles, a Wright Flyer. It's an aerospace orgy.