A STOL aircraft requires a level of design and performance integration beyond that currently involved in commercial transport aircraft. Each vehicle concept uses the propulsion system to provide a substantial portion of the low speed aerodynamic lift. This fact makes engine dynamic performance have a strong influence on the handling qualities and performance of the aircraft, as does the aerodynamics on the proper engine cycle for the best mission performance. The airlines equally have requirements which place demands on the technical ingenuity of the designer. These requirements may be overlooked in initial design studies. To preclude this oversight, the airlines' powerplant requirements are discussed from an airline point of view with major emphasis placed on propulsion subsystem design responsibility, engine selection, thrust deterioration, and maintainability.