Area 51
This infamous military base that had hordes of people planning to storm it in 2019, hoping to catch sight of extraterrestrial evidence, is a no-fly zone like several other military locations. The area around it is restricted to most, but not all, air travel.
The only commuter flights allowed to fly to Area 51 must originate from a specific terminal at a specific airport (Las Vegas’s McCarran International Airport). The planes themselves must use the call sign “Janet” to get clearance to enter the airspace.