When the AAR is reduced by the supporting ATC facility, the Air Traffic Control System Command Center (ATCSCC), in Warrenton, Virginia (Vint Hill Farms Station) institutes a Ground Delay Program.
Ground delay programs (GDP) can affect various sections of the United States' airspace, as well as airports in Canada.
Sometimes the scope of the ground delay programs is set by mileage; that is, all departures that are less than 1,500 miles from the affected center can be included.
These programs usually last for several hours and average delay minutes can vary as conditions change at the said ATC controlled area.
This is when the ATC facility can accept more traffic or users; that is, airlines cancel flight plans, thus causing openings.