All Smithsonian museums are free to the public. This one requires you to sign up online for a free pass to gain admittance. I was there August 3rd and I was fortunate that the security specialist gave me an extra pass. It's crowded but worth the wait.
Free but they booked online through mid Nov as of last week. You can also go and try to get same day entry when they release tickets at 1pm. That's how I got in but it was a Tuesday and there was still a long line.
True
Free, but lines are long. Get your tickets online in advance.
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