In January 1990, a major airline made a promotional offering to its frequent flyer members: "Fly three round trips from a hub city, and earn a free round-trip pass." American Airlines, wanting to gain a competitive edge, reacted rapidly by offering its frequent flyer customers a more progressive offering. Marketing offered a free round-trip domestic pass to any AAdvantage customer flying three round trips anywhere in the entire American Airlines route network, the awards to be mailed in May 1990. Round-trip identification had not previously been solved by a computer automation method because of complexities introduced by inconsistent or missing data. Historically, airlines have based the calculation of frequent flyer awards on the number of segments, segment miles flown, or specific (that is, hub) city activity. Offering round-trip promotions held the potential for opening a new era in frequent flyer competition and tipping the edge toward the airline that could make the offer. In late January 1990, the Sabre Computer Services department initiated a joint effort (traditional data processing staff and knowledge based systems staff) aimed toward developing a system that could identify round trips. This system, a response to a competitive market situation, was intended for use against the frequent flyer customer database. The effort consisted of the traditional application development support group defining and developing the methodologies for the extraction of data and the compilation of award certificates, and a knowledge engineer from the knowledge system group developing an expert system solution for the round-trip identification problem. Ultimately, an expert system that resolved the round-trip identification task was designed, developed, and implemented by the May 1990 deadline. The problem required the pattern processing of, and inferencing on, nearly 10 million data records. The objective, automating the identification and classification of a variety of round-trip types and minimizing a need for human intervention, was achieved.