Execution planning at the military airlift command of the US Air Force involves updating the routes and schedules of aircraft to reflect changing requirements for moving freight and personnel and changing airlift resources. The problem can be characterized as a pickup and delivery problem with time windows and node capacities. The constraints on the capacities of the nodes (airfields) limit the rate at which the aircraft can be serviced and the amount of requirements (tonnage of cargo, number of passengers) that can be loaded and unloaded at an airfield per day. The execution planning algorithm described can be used daily to modify the existing airlift operations plan. An algorithm based on the insertion heuristic was selected for implementation due to its computational feasibility and its capability to absorb complex constraints arising in the execution planning problem. The insertion heuristic has the additional desirable feature of keeping intact as much of the existing schedule as possible.
A typical airlift mission carrying troops and cargo to the Persian Gulf required a three-day round-trip, visited seven or more different airfields, burned almost one million pounds of fuel, and cost $280,000. During Operation Desert Storm, the Military Airlift Command (MAC) averaged more than 100 such missions daily as it managed the largest airlift in history. By August 7, 1991, more than 25,000 missions had moved more than 966,000 passengers and 774,000 tons of cargo to and from the Persian Gulf region. Each mission required scheduling aircraft, crew, and mission support resources to maximize the on-time delivery of cargo and passengers. To meet this challenge, MAC worked with the Oak Ridge National Laboratory to develop and deploy the Airlift Deployment Analysis System (ADANS). Within three months, ADANS provided a set of decision support tools to manage information on cargo and passengers to be moved and the available resources, as well as tools to schedule missions, to analyze the schedule, and to distribute the schedule to MAC's worldwide command and control system.
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