There's a joke within the ranks of flight attendants that typifies the sentiments of the passengers they serve: "No wonder flight attendants look so young -- it's all the preservatives they eat in the airline food."

Yet the feeders of the flying public say that the serving of an estimated 150 million meals a year is not nearly as simple a task as appearances suggest.

In addition to contending with the food preferences of everyone from children to vegetarians, these caterers to the masses serve meals, noted one executive chef, that "must be transported over roadways, placed on airplanes that shake, held for three to four hours and maintained at a proper temperature," for eventual reheating, reconstituting or finishing off by flight attendants in a tiny galley thousands of feet in the air.

"Airline food goes through a tremendous amount of abuse, unlike in restaurants," lamented United's Edgar Bader, executive chef at Washington's National Airport.

And, what may have looked and tasted good on the ground doesn't necessarily fly well. Certain types of fish (pompano, grouper and scallops, for example) tend to reek in the close confines of an airplane. Ditto sauerkraut if it's not prepared with great attention.

Peter Johnsen, an associate member of the Monell Chemical Senses Center in Philadelphia, suggested that the airline catering industry's biggest obstacle might be that of WOF (warmed-over food) in which institutional dishes cooked with fats and oils develop off flavors when reheated. "Mystery meat is not a college joke," said Johnsen, who added that WOF is currently considered by the meat industry to be its number one problem. Reheating, noted Johnsen, can result in the initial cardboard taste associated with foods that are cooked, held, and warmed for presentation.

Moreover, a traveler's sense of taste is probably affected as well by circumstances of ambiance and anxiety. "The difficulty in mechanically consuming the meal, three people in six feet of space," is as likely as anything else to contribute to a modification of appetite, offered Johnsen, who added he would like to compare the meal acceptance records of coach versus first-class passengers, who enjoy more space. And given an airplane's lower humidity level, dehydration, especially on flights of long duration, might also affect perception, Johnsen said.

It's the comparison with restaurants -- fair or not -- that caterers and food service personnel face in feeding the airborne masses. "We're always trying to be a restaurant in the air," said Carlos Bragado, director of in-flight services planning for Pan Am, which serves an estimated 10 million meals annually. "That's a pretty big restaurant."

Yet unlike a restaurant, said Wolfgang Diehl, Eastern's director of food services, passengers can't simply walk out if the dining experience is less than satisfactory. "It's different than at home or a place of your choosing. It's a controlled environment, a strange environment."

In some cases, flight kitchens are subject to local, state and federal health inspections, in addition to being monitored by officials from the individual airlines they service. The FDA requires that in-flight meals be maintained at one of two temperature ranges, either chilled (45 degrees or below) or heated (above 140 degrees). The chilled state is the one in which the tray set-ups (everything except the entree, which is handled separately) are stored prior to boarding, which explains why the silverware is generally cold and warm rolls are all but impossible to find in the air.

What we pick at aloft with those cold utensils is determined primarily by three factors: the time of day, the length of the flight and "the market," a term that covers an airline's budget, its competition and the regional preferences of passengers.

The market determines, for instance, that less fish be served on flights originating from the Midwest, that the meals on a flight from Puerto Rico to Miami be half ethnic, half American-style, or even whether a meal or snack should be served.

From that point, the executive chefs and food service directors work with the caterers, sometimes as much as a year in advance, to develop a product that is identifiable ("no mystery meats or sauces," explained one chef), consistent, varied and within the budget.

Some airlines have test kitchens, where an entree's durability is tested by simulating in-flight conditions. "We buy the best, knowing we're going to put it through its limits to make it palatable," said Bob Arnold, national director of food and beverage for Sky Chef catering. And almost all large carriers recruit management personnel, flight attendants and sometimes unsuspecting passengers in the testing stages. At Northwest Airlines, the top brass, including the company president, personally tests representative meals from each of 14 categories before they're served in the air.

Ultimately, it's up to the vendors (from whom caterers purchase ingredients or complete entrees) and the caterers (who actually prepare the meals in flight kitchens) to meet the specifications of individual airlines. No detail is too small to be overlooked; airlines deliver instructions for absolutely everything, from portion sizes to the color of the tray liners and the kind of salt used. (Like their passengers, even the airlines have become more weight conscious: every ounce, including lighter foodstuffs and utensils, counts in cutting fuel consumption.)

United, in contrast to airlines that contract for a majority of their food services, is one of the few airlines that are able to sustain a profitable catering division within the company; United prepares 70 percent of the meals served throughout its route system. Pastry shops in United's kitchens in Chicago and San Francisco produce almost all of the airline's bakery needs. And in a number of competitive caterer markets, United provides the meals served aboard Eastern, USAir, British Airways, Sabina and other rival airlines, although the meals are prepared to the buyers' specifications.

Most airlines rotate their menus on four cycles of from one to three weeks each, with the overall menu changing annually, to avoid "menu fatigue," a condition described by Peter Wetli, director of dining and cabin services for USAir, as the point at which "a meal is flown and flown and flown and the businessman says, 'Oh, that again'." Connecting cities are on different cycles to lessen the chances of a passenger encountering the same meal.

"Most coach meals are prepared by frozen food manufacturers, in such a quantity and under such government control that caterers couldn't do that," noted Eastern's Diehl. First-class meals, fewer in number, are generally made in caterer kitchens. "Twenty years ago, a lot was boarded fresh," explained Bader of United, "but that was before inflation, . . . we were serving less passengers then."

Additionally, "the price of a ticket is a new factor," said Wetli. "Passengers want more than a seat, so regardless of the time of day, officials think, must they put something on board?" Noted Carl Baber, United's director of food service planning, "There is a history of meals on planes; on an airplane, people want to eat more -- you'll eat at 10 a.m. if it's put in front of you."

Contrary to the stereotype of a sky filled with frozen TV dinners, not all airlines are dishing up a lot of frozen meals. Delta, for example, avoids using composite meals, which are vendor-prepared entrees shipped frozen to the caterer, who simply pops the item onto a tray for heating. Instead, said Charles Doherty, Delta's director of dining service, "all our meals are prepared from scratch . . . we do one meal a thousand times as opposed to doing a thousand meals at once." Pan Am takes advantage of its extensive international route system by employing local chefs to prepare meals for its first-class passengers. In Buenos Aires, where Swiss Air is contracted to service Pan Am, first-class passengers have the option of selecting a Swiss menu.

Yet Eastern's Diehl, whose airline uses composite meals, insists that improved technology has enhanced the quality of the frozen offerings. And at any rate, he noted, "we use first-grade [ingredients] only; we can't take chances with lower." Said Jim Jette, Republic's director of food service, "We need to compare the positive of fresh versus the continuity offered by the frozen food vendor. Food is a lot like making love -- you never do it the same twice."

Airlines have different ways of gauging the success of their meals, with comments filed by passengers and flight attendants being the most obvious. USAir monitors its food service via "meal acceptance reports," in which the trays from inbound flights are evaluated for signs of waste. Another airline, in more casual terms, refers to its evaluation procedure as "garbology."

Low public acceptance, along with problems in maintaining consistency, eventually results in an item's being pulled from the menu. Hence, Delta's lasagna is no more, and Eastern's French toast has been replaced with blueberry pancakes. Pan Am discovered that its passengers were more interested in a hot breakfast than a cold one, so it changed its menu on long-haul flights to reflect the preference. Cre pes have gone the way of the prop jet on Republic. And perhaps it was passenger patriotism that led to United's withdrawing imported cookies as a dessert offering: An American brand currently flies the friendly skies.

Most airlines are quick to refute the notion that lower air fares result in reduced in-flight food service, especially in the short term. "Our reputation is built on passenger perception," noted Pan Am's Bragado, "and it would take a hell of a long time to regain that if it was lost." Noted Eastern's Diehl, "it would be unfair to those who flew before and after [the price reductions]."

But somewhere the bottom line prevails, and perhaps the rosettes of butter are replaced with pats of the stuff. "Food is the first to go," said one airline chef. "We're not in the food business, we're in the flying business," he added. "But if the fare is the same price, you go with the one with the better meal."

Picking up on changing American eating habits, and what passengers conseqently might consider better meals, airlines are serving more soup and sandwich offerings, more pasta dishes, more poultry and less beef. Heavy sauces have all but disappeared from the menus. And hard liquor consumption is down, noted food service directors.

On the other hand, increased sophistication among passengers has paved the way for in-flight wine tastings, the expanded use of regional foods prepared by local talent and a return to the serving of fresh food where possible. Republic is currently exploring the possibility of serving Cajun-style fare, "despite the labor-intensity of blackened redfish," noted Jette.

To remain competitive, the major carriers all offer a variety of special meals, covering a range of dietary and religious needs (vegetarian -- both pure and lacto/ovo -- diabetic, low-cholesterol, low-sodium, low-calorie, low-fat, children's, infants', bland, Hindu, Moslem), as well as alternate selections -- fresh fruit plates, seafood platters and the like -- for passengers who request them at least six hours in advance.

The seafood and fruit entrees aren't given much publicity -- airlines aren't desirous of having to serve these costlier alternatives -- but in this case, the difference between a first class and a coach class meal can be little more than a garnish of parsley and a few extra shrimp or fruit pieces. At any rate, special meals account for approximately 2 to 5 percent of all in-flight meals that are served, often including one up front.

For anyone who has ever wondered what would happen in the event of food poisoning at 32,000 feet, rest assured that what was originally viewed as a status symbol is now generally regarded as a safety precaution: of the meals served the cockpit crew, one is almost always different.