Hi Kirk,
There could be many reasons but I can give you one I have at the moment.
I have been asked to video a military band whilst they rehearse on a parade ground in front of a beautiful barracks building.
The shots I will be able to get will be fantastic. I will be doing a three camera shoot - one locked off, one handheld and an aerial platform. I will be able to fly over the barracks to a reveal shot of the band in full military dress performing. Additionally, doing close low passes over their heads as they march under the Inspire. These shots would be impossible to get even with a crane.
The only problem I have....... The parade ground is located on a military base and, you guessed it....its a NFZ.