Guns aren't 100% banned in airports. In Northern Wisconsin, we get people checking firearms all the time during the hunting season. There are also provisions for passengers carrying firearms (most people cannot do this, of course, but there are a few exceptions out there). Also, our airport's terminal had finished remodeling and the secure area was open during an open house. Of course, this wasn't during flight time, and the TSA had to allow for it and (I'm sure) scan the place for unallowed items after, but I'm sure it wasn't too hard to do that for this video.