C1.8.7 STEP 6g — Holding Aprons
Holding aprons can be placed at a convenient location on the airport for the temporary storage of aircraft. These can be required at large airports where the number of gates is insufficient to handle demand during peak periods of the day. If this is the case, aircraft are routed by air traffic control to the holding apron and are held there until a gate becomes available.
Holding aprons can also permit a departing flight to vacate a needed gate and to wait near the runway without obstructing either the arriving aircraft onto stand or the departure flow, pending receipt of ATC/ATFM (slot) en-route clearance. They can also be used for aircraft with long turnaround times, where staying on stand would unnecessarily tie up capacity. This is particularly true of airports where contact stands are limited.
Holding aprons are not usually required if capacity slightly exceeds demand. However fluctuations in future demand are difficult to predict, and therefore a temporary holding facility may be necessary.