TURNED OFF by tasteless airline meals? By gray, overcooked vegetables, starch-laden casseroles covered with brown library paste, steaks branded with lines to make them look as if they had been grilled when instead they had been stewed, gummy salad dressing and desserts that taste only of sweetness?

You can always reject the meals and chew you nails while everyone else eats. Or you can try one of two other alternatives: Order one of the special meals prepared for dietary or religious reasons and hope for the best; or bring your own picnic basket.

Depending on where you are catching the plane, because different caterers service airlines in each location, the first may be satisfactory. But without a doubt, if you want to eat well, you'll have to do it youself.

Most large, domestic and foreign airlines offer a selection of alternative meals for people who cannot eat the regular meals, usually because of some health or religious taboo. While United Airlines appears to have the most extensive set of specifications for supplementary meals, most airlines say they will try to accomodate if the passenger will specify what he or she cannot eat. El Al claims to have invented special diets. With tongue in cheek, the public relations director of the Israeli airline, J. Peter Brunswick, says: "It is second nature for a Jewish airline to worry about diet."

Many of the airlines have specifications covering the following diets for health reasons.

Bland - which means no seasonings and emphasis on milk products. Asked about El Al's special meals for bland diets, Brunswick might have been speaking for the majority of the other carriers, when he said: "Most people think that's what our meals are anyway!"

Diabetic and hypoglycemic - low in refined carbohydrates.

Gluten-free - no wheat products.

High protein. At one time, according to a Continental Airline spokesperson, "experienced travelers found out that by asking for high protein meals they would get a steak or seafood platter but now they are out of luck. They get cottage cheese."

Lactose restricted - no milk products.

Low calorie and Weight Watchers. In addition to low calorie food, some airlines offer a meal officially approved by Weight Watchers.

Low Cholesterol, Low Fat, Low Protein and Low Sodium.

Continental includes a card listing the grams for fat, carbohydrates, protein and salt on special diets.

For various religious taboos there are a number of meals, kosher being the most in demand. A kosher meal would be free of pork and shellfish. Meat and dairy dishes would not be mixed.

If you request a Hindu meal, the airline may give you a vegetarian meal or one without beef or pork products. According to TWA's specifications, the airline would try to serve you a curried dish if it were available from their local caterer. Restrictions for Moslem meals would eliminate pork and shellfish as well as alcoholic beverages.

United also has specifications for Oriental meals - stir-fried food with "slightly undercooked vegetables" - and for Soul food - hot sauce and "home cooking" (whatever that means on an airline).

Vegetarians are broken down by some airlines into two categories: lacto-ovo, those who will eat milk products and eggs, and vegan, those who eat no animals products of any kind.

There are also meals for children: hot dogs, canned spaghetti and meat balls, fried chicken, hamburgers and cold sandwiches like peanut butter and jelly. Each airline offers some of the above. In addition, many have processed baby food.

Some airlines like Continental and American offer special menus to their regular travelers who "might get bored with the sameness of the meals." The alternatives include chefs salad, Reuben sandwich, fruit salad, hamburger.

These airlines, along with Delta, Eastern and TWA, include vegetables and/or fruit plates as laternatives. A fresh fruit plate can be quite good on a flight orginating from California, but think twice about it if the flight originates in Minneapolis in January.

Most airlines prefer to have special meal requests ordered when the reservations are made, but some meals can be provided by some airlines with as little as four hours notice.

If you still feel that airline food is going to taste like airline food no matter how specialized it is, you can always brown bag it.

Certainly on one of those economy flights where meals are extra anyway, it's better to do it yourself. Skytrain charges $3 for a cold supper, 50 cents for drinks. Other airlines, competing with Skytrain, have begun to offer similar no-frills service. Skytrain's originator, Freddie Laker, told a group of industry officials in Washington recently that about half of his passengers don't even buy the meals. "Just think how much money is wasted every day by the airlines of the world carrying food no one wants," he said.

El Al's Brunswick thinks air travel without meals is the wave of the future and "a blessing in disguise. I'm so sick of airline meals and complaints," he said.

"Airlines have given all services that other means of transportation have always charged for. Airlines can't raise fares very much more. On the contrary. And when the fuel squeeze starts again - and it will - airlines will have to cut somewhere. There are few other places to cut."

While you still have the option, and want to bring you own lunches and dinners, there are some simple guidelines to make it easier.

Try to select food with few "remains." And cut the food into individual portions in advance. As much as possible should be disposable with the possible exception of the corkscrew and the carrying case that might double for other purposes when you get where you are going. Otherwise, a sturdy paper shopping bag is perfect, plus a sufficiently large plastic bag for disposal.

Choose things that travel well. Leave the barbecued spareribs, dripping in sauce, or the cream-filled Napoleons at home. Home is where the smelly things like fish and dead-ripe Brie also belong. Have pity on those sitting near you.

While you can buy an individual bottle of wine, already wrapped with its own plastic glass, the selection is very limited. You might as well carry a cork-screw and choose a bottle that suits you. If you are drinking a white wine, which must be chilled, you will need either one of those flexible thermal containers or a heavy-duty plastic bag filled with ice.

You check list should include: an ample supply of large paper napkins, plastic forks, knives and spoons, plastic glasses and paper plates.

Condiments can be packed in small plastic containers or in securely tied plastic bags.

While you can carry aboard hot coffee or tea in an insulated container, more than likely the airline will provide if either free or for a small fee. Let them.

As to what you ought to eat on this picnic in the sky, your pocketbook is your guide. If you are trying to save money, you'd be better off cooking the food yourself if you have the time. The easiest way is just to make an extra amount for your final dinner at home and take the leftovers of the roast chicken, beef or - best of all - meat loaf.

Stay away from the tuna and chicken salads made with mayonnaise, unless you can keep them at refrigerator temperature until it is time to eat. Otherwise, your first stop after you leave the plane may be a hospital bed.

If you have no time to cook and want to keep costs down, buy some cheeses, good French bread, and prepared salads made without mayonnaise, like Greek or marinated bean (drained off most of the liquid). Add some cherry tomatoes, olives or other pickled or raw vegetables. For dessert, a piece of fruit or a few cookies or brownies.

If money is no object for your picnic aloft, a phone call or trip to your favourite gourmet shop before you leave will help you to indulge you flights of fancy. Foie gras, pates, terrines (and don't forget the cornichons), caviar, smoked salmon with lemon wedges or bagels and cream cheese, thinly sliced country ham with Gruyere, and a bottle or two of Perrier along with a few exquisite bite-size French pastries.

Brown-bagging it at 30,000 feet isn't really much different from a picnic in the country - except for one grand bonus: There are no uninvited guests marching across your tablecloth or swarming over your head.