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Milestones of domestic air transportation in the past 50 years are highlighted. Many early innovations were of European origin. Lindbergh’s flight accelerated the use of airplanes as a means of domestic transportation. The DC-3, prior to World War II, achieved a high degree of standardization and established a foundation for future airline growth. After World War II, converted military transports were primary means of conveyance. Phenomenal growth of air travel is due to increased speed, safety, and comfort brought about by use of four-engine planes, automatic pilot, cabin pressurization, and improvements in electronic guidance systems. Basic problems such as over-capacity, need for greater standardization, better ground facilities, and efficient servicing of local air traffic face the airlines today.

The flight problems of clear air turbulence are brought into focus. The forecast problem is reviewed and airline practices in forecasting are described. It is demonstrated that adding the requirement of an axis of minimum temperature at levels from 300 to 200 mb reduces the average forecast box appreciably as well as adding accuracy. A practical forecast procedure is suggested.

Certain atmospheric temperature changes have been observed to be a factor in detecting the occurrence of clear air turbulence, especially at jet altitudes above 25,000 feet. Data for this study were collected on 146 flights during the year while riding as an extra crew member in the cockpit of airline and military jet aircraft. The aircraft instrumentation in the research program included a portable test instrument to detect temperature changes as well as the normal components of an air data system and temperature sensors. A comparison between several rates of temperature change was made in an effort to determine which would indicate actual flight conditions most efficiently. From flight observations using the portable test instrument, a rate of temperature change of 1.0°C per minute was found to be the most useful criterion for correctly indicating flight conditions in the majority of cases.

When an airline finds itself in trouble with an engine because of high cost or poor reliability, or both, decisions frequently must be made long before a complete picture is available to the decision makers. Experience and judgment play a major role in selecting the course of corrective action. This paper reviews these difficult decisions in a specific case history. The results of those decisions are analyzed quantitatively and the significance of the results discussed qualitatively. A relationship is then drawn between the operators’ experiences and the design criteria established by the engine manufacturer in the design of new engines.