Airline crew members and passengers may face a new hazard: ozone sickness, which has apparently struck hundreds of people during recent flights.

Ozone gas is in a layer of the earth's atmosphere; normally it has been far too high to cause any problems for airline trips. But now it has apparently been causing illness because airplanes are flying higher to conserve fuel and because the ozone has dipped closer to earth.

Whether low doses of ozone cause any long-term effects isn't known, doctors say. But in the short run, enough ozone in the air can trigger a racking cough that may last for hours, severe shortness of breath, headaches, fatigue, eye irritations and sometimes bloody noses. Describing one recent flight, a Pan American World Airways stewardess says, "Almost everbody in the cabin was coughing and wheezing - the place looked like a tuberculosis sanitariam."

When the ozone sickness first struck, apparently a few months ago, no one knew what it was. The symptoms, however, are setting off myriad repercussions:

Squabbles between pilots and stewardesses over what has been happening and what to do about it have been brewing on planes.

A scientific detective hunt has been under way to track down and confirm the cause.

A scientific detective hunt has started, mainly by Boeing Co. and Pan American, to try to remedy the problem.

The airlines haven't made public announcements about the ozone sickness, apparently fearing that they might scare passengers away. (Crew members interviewed generally asked that their names not be used for fear their comments would upset management.) When asked about the problem, company executives emphasize that they are working hard on remedies. "We think we're on the road to a solution," says William Waltrip, Pan Am's executive vice president for operations.

The normal oxygen molecule consists of two oxygen atoms, while the ozone molecule consists of three. The airline ozone problem isn't restricted to a particular type of aircraft. United Airlines, for example, says scores of people on 35 of its coast-to-coast flights have been hit by the ozone sickness. The flights were in Boeing 747 jumbo jets and McDonnell Douglas DC-8s and DC-10s.

Man recent cases of the illness, however, appear to be on board Pan Am flights from New York, San Francisco and Los Angeles to Tokyo. These flights use the Boeing 747 SP (the initials stand for "special purpose"). The SP flies farther and higher than most other planes. For example, a medium-size jet such as the 727 typically flies for two hours at 35,000 feet on a New York-Chicago run. On a New York-Tokyo nonstop run, a Pan Am SP flies nearly 14 hours at around 45,000 feet. The high altitude, which conserves fuel, and the long distance combine to increase exposure to the ozone high in the earth's atmosphere.

Last year, when Pan Am became the first airline in the world to introduce the SP on its routes, stewardesses were the first to begin complaining. At first, ozone wasn't even suspected as a cause. "It's a long flight to Tokyo, through numerous time zones and your body gets all out of synu so you expect some minor problems," says William Lindner, director of safety at the Transport Workers Union, which represents Pan Am stewardesses. Pan Am's initial reaction to the complaints, Lindner adds, was that "well, some people are hung over." And he says, "I think management also suspected some union tactics may have been involved."

The stewardesses weren't sure what was happening. "The girls don't like the SP anyway because the flights is so long and the air is so dry you become dehydrated," one Pan Am stewardess says. "At first even I thought it must be psychosomatic."

But the number of complaints began rising - and in strange ways. "People seemed to have trouble going out to Tokyo, but not coming back," Waltrip says. "We couldn't figure it out." Pan Am then began monitoring temperature and humidity in the cabin, correlated with latitude and longitude, to seek clues to what was happening. Ozone, not being suspected, wasn't measured.

In January, however, the complaints skyrocketed. "Previously we were having trouble on six to nine flights a month, but beginning in January it went to 12 to 18 flights a month," Waltrip says. As Lindner of the transport unions puts it; "At the start of January, all hell broke loose; over a period of months we've gotten hundreds of complaints."

Many pilots, however, still weren't affected, and some wouldn't believe that the stewardesses were encountering a real problem. "They told us we were just a bunch of hysterical women," says one stewardess.

(As it turned out, stewardesses were the first to notice the ozone problem because those who are physically ac-active - say, in serving meals - are affected more than those seated, such as pilots and passengers. Flights to Tokyo were affected more than return trips because wstbound flights, also fly closer tot he North Pole; zone is closer to the earth at the North Pole than it is farther south. In other quirks, ozone affects nonsmokers more than smokers and affects the young more than the old; alcohol in creases ozone's effects)

Complaints became increasingly severe. In March, "we were four hours out (on a flight from Los Angeles to Tokyo) when I began coughing," one Pan Am stewardess says. "I cughed for two hours straight - a deep, hacking cough like bronchitis. It stopped for a while, and then I coughed for another hour, and I was coughing up phlegm with specks of blood in it." When she arrived in Tokyo, she says, she went to bed and slept for 12 hours, and only then felt normal.

On another Pan Am flight, one businessman began suffering shortness of breath. According to a stewardess on the flight, "he was kind of gasping and he told me. It feels like a heart attack coming one."

Pilots on Pan Am and United began encountering the symptoms. An inspector for the Federal Aviation Administration, which oversees airline safety, boarded a Pan Am SP flight. The inspector got sick, with coughing, mild chest pains and dry nose tissues. It was "a pretty bad case," an FAA spokesman says.

Airlines stepped up their air samplings, and this time they included a measurement for ozone. Even before the airlines' problem had cropped up, the Occupational Safety and Health Administration had been proposing that industrial workers not be exposed to ozone concentrations averaging higher than 0.1 part per million (ppm) during an eight-hour period. According to Pan Am, its measurements soared up to 0.6 ppm.

The airlines quickly took some interim steps to ease the situation. They suggested that pilots encountering problems reduce their altitude to avoid the ozone. On March 26 United Airlines sent an internal message to crew members. If symptoms develop "pilots should immediately don their oxygen masks, select 100 per cent [oxygen] and continue to use the system until the symptoms are relieved. . . . Flight attendants can alleviate discomfort by breathing through a wet cloth or wet paper towel held firmly over the nose and mouth. Passenger symptoms can be relieved similarly." United added: "Airlines have flown upward of 100 million hours on jet aircraft since they were introduced in 1959 and this is the first time something of this nature has been reported."

But the problems have been continuing, partly because the ozone layer shifts and isn't easy to track and avoid "Fingers" of ozone may point toward earth; Boeing says some airlines have reported cases of ozone sickness as low as 37,000 feet on domestic flights.

In addition, some pilots still scoff at the problem. J. F. Garfield, a Pan Am captain and a member of the aeromedical committee of the Air Line Pilots Association, says ozone "doesn't look like a serious thing. The power of suggestion among the girls is terrific. It's like among high-school kids; when one faints, they all start fainting."

Stewardesses maintain that some pilots aren't willing to reduce altitude because they want to conserve fuel. According to one Pan Am stewardess, on a recent flight the pilot wouldn't descend even though "lots of people were coughing badly." She adds: "The people were frightenend. After a few hours you get claustrophobic on those long flights anyway, and then, when you find you have trouble breathing . . ." A Pan AM spokesman denies that pilots are refusing to cut altitude.

The stewardesses also say they are having trouble doing their work. "I've seen girls incapacitated - they just have to sit down and put their head between their legs. But it's our job, and most of us just keep stumbling through," one says. Another Pan Am stewardess says flight attendants are trying to switch the work load, performing the heavier work, such as serving the main meal early in the flight and trying to rest more later when the ozone sickness is more likely to hit.

Pan Am is working on solutions better than simply reducing altitude. The air in a plane's cabin is brought in through compressors in the engines. If the air is taken from a hotter stage of the compressors, the heat breaksdown the ozone, eliminating the problem. During a recent test flight over Montreal, Pan Am says this method cut the ozone from 0.4 ppm to under 0.1.

The problem with this solution is that using hotter air to break down ozone instead of driving the jet engines imposes a fuel penalty of about 3 per cent. Pan Am burns 910 million gallons of fuel a year, and at that rate 3 per cent is "damned expensive," says Waltrip.

As a result, Boeing is trying to find a filtering system to block zone intake. Boeing isn't talking about its tests, but one airline source says that Boeing tried copper filters that "looked like Brillo pads" and that they didn't work. Boeing has also been trying cotton, glass-fiber and charcoal filters, it is understood.

The problem could go away by itself, at least for this summer. The ozone layer may be lower this year because of the cold weather this past winter. A hot spell may drive it above even the highest airline flights, at least for a while.

Those encountering ozone sickness, meanwhile, seem to be recovering within a couple of hours after a flight. United has been giving a battery of medical tests, including chest X rays and pulmonary-function tests, to stewardesses after they have been sick. Dr. George Kidera, United's vice president for medical services, says that thus far the tests haven't turned up any ill effects.

But there is still concern. Ozone in high concentrations is widely used in the chemical industry, and doctors know that at extremely high concentrations - say 10 ppm, or 100 times the OSHA recommended level - ozone can cause swelling in the lungs, bleeding and death. There are also studies, mostly in animals, suggesting that even at low concentrations, ozone might cause serious cellular damage.

But long-term studies in man are few. "Little is known about chronic exposure to very low concentrations such as might be expected to occur in air crews flying frequently at high altitudes," says Siegfried Gerathewohl, chief of research planning at the FAA's office of aviation medicine.

Despite the problem that ozone poses for airlines, it plays a beneficial role in that it shields the earth from much of the sun's ultraviolet radiation, which can cause skin cancer. The fluorocarbons contained in many aerosol sprays are facing a ban because these chemicals waft upward and pose the danger of destroying a portion of the protective ozone.

Because of then worries for aviation, Boeing and the airlines are pushing as fast as they can to find a good solution for the problem. A Pan Am stewardess, boarding a flight to Tokyo a few days ago, told a reporter: "This is our best plane - it has all the latest gadgets to take care of the ozone." She added hopefully, "Maybe we won't have any problems this flight."

The Concorde supersonic transport, which cruises at up to 60,000 feet, hasn't run into any ozone problems.

The reason, says an official of British Aircraft Corp., which helped build the plane, is that the Concorde was designed to eliminate the ozone problem. The Concorde achieves this by bringing air into the cabin from a very hot stage of the engine's compressors. The heat breaks the zone down.

Concordes are flown by British Airways and Air France.