 Similar in intent to the scrambling of military aircraft, the hot-spare program is designed for a flight crew to takeoff with an empty aircraft within 30 minutes of a request for service.At any given time, 14 different aircraft are designated at 7 UPS Airlines hubs, equalizing flight distance and time between locations.Four of the six aircraft types flown by the airline are used for hot-spare service (excluding the 747-400 and 747-8).