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The stand-allocation system (SAS) is an Al application developed for the Hong Kong International Airport (HKIA) at Chek Lap Kok. SAS uses constraint-programming techniques to assign parking stands to aircraft and schedules tow movements based on a set of business and operational constraints. The system provides planning, real-time operation, and problem-solving capabilities. SAS generates a stand-allocation plan that finely balances the objectives of the airline-handling agents, the convenience of passengers, and the operational constraints of the airport. The system ensures a high standard of quality in customer service, airport safety, and use of stand resources. This article describes our experience in developing an Al system using standard off-the-shelf software components. SAS is an example of how development methodologies used to construct modem Al applications have become fully inline with mainstream practices.
Costing over US$20 billion to construct, the Hong Kong International Airport (HKIA) at Chek Lap Kok replaced the old airport at Kai Tak, which was already one of the world's busiest international airports in terms of its passenger and cargo throughput. Although there were some initial hitches when the new airport opened on 6 July 1998, operations quickly returned to normal within a week's time. Within a month, operational statistics surpassed those of the old airport-80 percent of all flights were on time or within 15 minutes of schedule, all passengers cleared immigration within 15 minutes, and average baggage waiting time was only 10 minutes. During the 1998 Christmas holiday, HKIA serviced about 100,000 passengers daily and maintained equally high service standards. In January 1999, Travel and Leisure Magazine awarded HKIA the Critics' Choice Award in recognition of its levels of satisfaction and praises received from travelers to Hong Kong.
The main responsibility of ensuring that the airport operates smoothly and that travelers are satisfied rests on the shoulders of the Hong Kong Airport Authority. The airport authority manages and controls all activities related to airport operations. It also has the responsibility of scheduling and managing all aircraft parking and ground movements at HKIA. On a daily basis, the airport authority assigns parking stands to aircraft based on the daily flight schedule, rotation information, and a set of operational constraints. It also schedules aircraft tows to optimize the use of inner stands. In...