Incorporation of an advanced technology, high-speed turboprop propulsion system into future air transports can achieve significant reductions in operating costs through large reductions in fuel consumption. Today’s turboprop systems exhibit propulsive efficiencies which are superior to current high bypass turbofans but are limited to lower cruise speeds, which are incompatible with market requirements and air traffic control environments. The propfan concept allows the superior propulsive efficiency of the turboprop to be extended to cruise speeds of the current turbofan aircraft. Fuel consumption and operating cost benefits are shown by comparison of a propfan and turbofan powered aircraft, each designed on an equal-technology and equal-mission basis. Projected 1990 time frame comparisons are also shown. The advantages of the propfan aircraft, in light of ever-increasing fuel shortages and fuel cost increases, have resulted in several NASA-sponsored research programs to verify propulsion performance and develop the required technology base. Continuation and escalation of these activities must be accomplished to ensure incorporation of the propfan into the next generation of commercial air transports.