ARO, or Airport Reservation Office, processes all requests for Instrument Flight Rules operations at high density traffic airports, and services John F. Kennedy International and La Guardia International in New York and Ronald Reagan Washington International in Washington, D.C. The Office also schedules landings at these airports by aircraft that are not yet scheduled for a landing time.
Due to the high traffic volume at these airports, the ARO must give permission to flights that need to use IFR regulations in order to stay in the flight pattern and eventually land. Because of the density of aircraft around these facilities, sometimes it is unsafe for aircraft to fly by IFR, in which case they may be turned away to an alternate airport.
The ARO schedules aircraft to land at these runways as well. There are only so many aircraft that can land at these airports in a single day, so landing times must be scheduled and strictly enforced. Delays can back up the entire airport. These landing allocations are only available on a first come, first served basis, so if a flight needs to land on a day when the airport schedule is full, he is usually out of luck unless it is a dire emergency.
Airport Schedules that are run by the ARO are usually also built up around holidays and special events, such as the Olympics, NASCAR, or Golf Tournaments. The skies can quickly fill with aircraft and the landing schedule is adhered to by the minute. The ARO helps to relieve this congestion and try to get the aircraft down as fast as possible in order to fill the demand for a clear landing runway.