This paper describes the comprehensive database developed by the Lockheed Aeronautical Systems Company which underscores (he critical mission needs for an Advanced Tactical Transport (ATT). A unique process was used to substantiate that an ATT must have the capability to: Deliver Army maneuver units and their fire support systems that weigh up to 55,000 lb. Operate on hot days, at night, or in bad weather from unpaved runways less than 2000 ft. In length at elevations greater than 4000 ft. Operate routinely within 20 nm of enemy Sines, and occasionally over enemy territory, and have improved survivability features. Accomplish multiple unrefueled sorties with total distances up to 1500 nm. Design implications, considering six specific alternative concepts, are discussed in terms of relative mission effectiveness, cost, supportability, survivability, technology and system programmatics. The database provided is adequate to enable affordability and operational policy considerations to be included in the requirements definition program phase.