I N his comment on the paper Advanced Subsonic Transports—A Challenge for the 1990's by Richard E. Black and John A. Stern, J. Mayers has made a strong and convincing argument for an increase in the level of government support for aeronautical research and development. No one can disagree with his position on this critical issue. However, reduced government research and development support for aeronautics is not the major reason for the delay in the appearance of an all new advanced technology transport. A change in the economic environment and the resulting impact upon the market for new aircraft is the major factor. Historically high rates of inflation combined with depressed economic conditions have characterized this environment. The domestic airlines have had to contend with lower passenger traffic growth rates and rapidly rising costs (Fig. 1). The international airlines have had the same general problem except that their individual costs have risen at different rates. Airline earnings and their ability to purchase new aircraft have been affected by these developments. Some airlines have experienced substantial operating losses over a period of years while others have experienced a continuing inadequate level of earnings. Slower traffic growth rates, combined with the uncertainty produced by an inflationary environment, cause both airlines and commercial aircraft manufacturers to emphasize economic factors. The average annual rate of U.S. inflation was 3.5 times higher from 1965 to 1975 than from 1955 to 1965. Technology advances, as applied to commercial aircraft, must result in increases in economic productivity which exceed the price increases caused by inflation. In earlier periods of commercial aircraft development, significant operational improvements, such as increased speed, range, and comfort, caused existing aircraft to become obsolete. In addition, operating costs were steadily decreased. With the advent of pure jet transports in 1958-1959, a new high level of comfort was achieved. Aircraft manufacturers, using available technology, have not yet found an economical way to significantly exceed the speed standards of those aircraft. Thus, new and more expensive advanced technology aircraft must offer significantly improved operating economics which offset adverse aircraft operating cost trends. The airlines usually will not consider re-equipping their fleets unless the aircraft manufacturer offers direct operating cost reductions on the order of 10 to 20 percent because of the high introduction cost of new aircraft. Therefore, since aircraft price is a major factor determining direct operating costs, the use of advanced technology must improve economic productivity commensurate with its cost, it must pay its way.