Why are there "No Fly Zones"?

No Fly zones or no fight zones are put in place for protection. They are in areas where planes should not be allowed to fly over. Mainly, the military set up these zones in order to protect special and important people or areas of the country. These no-fly zones may be put in place for a major event like the Olympics or World Cup in order to discourage terrorists from flying in there.

The results if a plane flies into a no-fly zone is to be shot down. This should deter terrorists from flying into a zone where a major event is taking place. The air traffic controllers will know to automatically shoot down any plane. They will not have to question them since it is only a matter of a few seconds before the terrorists could do significant damage.