NKC airport
Like many other airports in that part of the world if the President was coming or going they would close the airport for all traffic. No Notams of course as this was always a "state secret". While I was flying there this would happen at least once every month. The only hint this would happen is if the "Band" would show up and start practicing.
Therefore don't plan landing on minimum fuel as you may need more to hold outside the control zone for an untermined time.
Besides that ATC was always friendly.