Airline executives, concerned about an imminent world shortage of pilots, are taking steps that will place younger and less experienced fliers in command of airliners.
The shortage, most apparent in other countries, is still a few years away in the United States, aviation experts say. But it has already caused a flurry of hiring by American carriers unseen in recent years that points to the coming scarcity.
''Ten years from now every airline in the country will have 30-year-old captains,'' said Capt. Vern Laursen, vice president for crew training at Trans World Airlines. Causes of the Threat
The reasons for the threat of a scarcity are numerous: the boom in the civil aviation industry; a soaring retirement rate among an aging corps of pilots, whom the Government requires to leave the job at 60; a decline in the number of new students taking up flying, partly a result of costs of basic training that have risen with liability insurance rates, and a lack of growth in the airlines' customary supply of aviators from the military, which has raised pay in an effort to remain more competitive with the carriers.
As a result of all these factors, the pool of experienced American fliers is drying up. ''The whole industry's pretty well employed right now,'' said Ed Muir of the International Air Service Company, which recruits crews for airlines. ''It used to be, a large percentage of pilots were unemployed.''
The employment boom is such that one-eighth of the 56,000 pilots flying large jets for United States airlines were hired last year. And these airlines expect to hire 32,000 more pilots in the next 10 years, says Future Aviation Professionals of America, a career information service based in Atlanta. Debate Over Safety
While the notion of 30-year-old captains may sound alarming to a public that has long equated gray hair in the cockpit with safety -two-thirds of major airlines' pilots are over 45 - most executives and other aviation experts contend that a new generation of young pilots is not necessarily a safety threat. Some even argue that younger, less-experienced pilots may be safer than their predecessors, because they will have learned fewer bad habits.
These experts caution, however, that the trend toward less experienced pilots means that the new aviators must be trained better from the first day. Others assert that even the best training is not always an adequate substitute for years of experience in the most demanding cockpit situations, particularly those requiring mastery of an emergency that could lead to an accident.
''If they've got enough training that they are a walking book of knowledge on that airplane, that can make up for experience,'' said Donald D. Engen, former head of the Federal Aviation Administration. ''But when push comes to shove, when everything turns to worms, experience is what really counts.''
The pilot hiring boom now under way is sending a number of ripples throughout the aviation industry, including these:
* Age, vision, height and weight restrictions that once kept many would-be pilots from the cockpits of major airlines have been loosened. Further, until three years ago most big airlines hired only college graduates; now one newly hired pilot in 10 has no college degree.
* Training programs are expanding, and students with little experience, especially women and members of minority groups, are being recruited to seek careers as pilots.
* The use of flight simulators and other computerized training devices is booming, with civilian and military pilots spending more and more of their training time on the ground. Some experts say this trend has gone too far, but officials of training programs are ecstatic at the chance to run rapidly through a series of exercises that would be dangerous in an airplane and that can be tailored to individual pilots' weaknesses. Paid Training a Trend
Paying nonpilots to learn how to fly has not caught on yet in the United States, but it is growing overseas, with carriers like Japan Air Lines, Lufthansa and Swissair training new fliers from classroom to cockpit. These carriers' experience may point the way for airlines in the United States.
In October, China Airlines, of Taiwan, sent 11 flight attendants and 13 other workers to the first class of a new flight school in Grand Forks, N.D., run by Northwest Airlines and the University of North Dakota. Gulf Air, of Bahrain, is sending eight more students this month. The airlines are paying the $67,000 cost for each student.
Capt. Y. L. Lee, director of training for China Airlines, said his carrier's students would spend 18 months in training in North Dakota and four more in Taiwan before going to work on 45-minute flights around the island.
Worried that a shortage is near, United and Eastern as well as Northwest have struck deals with universities or colleges to help run aviation programs aimed at producing professional pilots. The F.A.A. and Northwest split the cost of a new $6 million aerospace center on the North Dakota campus.