A desert 30,000 feet in the air

The atmosphere in the passenger cabin of a modern jetliner is pressurized, filtered and warmed to make fliers feel right at home. Unfortunately for fliers from around these parts, the airlines generally interpret home as being someplace high and dry, like Flagstaff, Ariz.

Most travelers will agree that they find the artificial atmosphere on an airplane to be considerably less than natural or comfortable. Couple dry, stale, thin air with jet lag, motion sickness and all the other medical complications that arise when sealing several hundred strangers in a small space and launching it through altitudes of up to 40,000 feet for hours on end, and it's easy to see why long flights can be a challenge, particularly for those with heart or lung problems.

With that in mind, here's a prescription of time-tested tips for in-flight comfort.

Despite cabin pressurization, or perhaps because of it, takeoffs and landings can be ear-popping experiences. For most folks, the pain can be subdued by chewing gum, sucking mints or sipping on something warm, like coffee.

Sometimes, however, simple measures just don't work. In that case, you might try a more aggressive approach. Ask the cabin attendant for a Styrofoam cup, a paper napkin and some hot water. Put the napkin in the cup, moisten liberally with hot water, and cup it over the ailing ear. The warm moisture should help unlock the blockage.

If you're already suffering from a sinus cold or allergies, try taking a decongestant tablet an hour before you get on the flight.

Dehydration is another concern in the desert-dry atmosphere, which sucks available moisture from your skin, eyes and every breath.

The obvious solution is to drink plenty of solutions. These days, it is entirely fashionable for travelers to tote along their own bottle of water or sport drink, from which they quaff frequently. On longer flights, however, that may not be enough. So say yes every time the cabin attendants offer beverages. Water or fruit juices are preferred, or noncaffeine drinks. One cup of coffee or tea won't hurt, though consumed in quantity, both are diuretics, which only exacerbate the dehydration, not to mention increase frequency of toilet visits. In any case, go easy on the alcohol; one drink in the air is worth three on the ground. And also, while sucking a mint or chewing gun to clear an ear is fine, it's better not to do either for too long in flight, as both tend to dry the throat.

If you're prone to suffer motion sickness, ask for a seat over the wing, where the ride tends to be the smoothest. Dramamine tablets or Scolpolomine skin patches can generally provide enough relief for even the longest flight.

Finally, one medical rule of thumb states that flying should be safe for anyone who can walk a block or climb a flight of stairs without becoming short of breath. But if you've suffered recent emphysema, heart ailments or gastrointestinal illness, consult your doctor before making plans to fly.

Travelers who require supplemental oxygen can usually make arrangements through the airline to have a tank with a supply sufficient for the estimated duration of their flight. For example, US Airways maintains a special Oxygen Desk to handle passenger needs on its main jet lines, both domestic and international. Oxygen is not available on commuter planes, shuttle flights or Metrojet departures.

The best time to place an order is when you make reservations, because passengers with oxygen can sit only in window seats. Reservations must be made a minimum of 48 hours before the flight, because the process involves a form that must be obtained from the oxygen desk, signed by your doctor, and handed in when you pick up the tanks at the special services desk. The airline will also need to know your required flow rate (2, 4 or 6 liters per minute). Each tank, which will last about three hours at a rate of 2 liters per minute, costs $75. Thus, depending on the traveler's need and the length of the flight, the cost for a 5 1/2-hour flight to the West Coast will be $150, in addition to the price of the seat. Oxygen charges are payable in advance and are nonrefundable.

Another problem results from sitting inactive in a cramped airliner for hours on end, which is uncomfortable and possibly even dangerous. Medical research indicates that sitting too long can cause dangerous blood clots to form in the legs, a condition known as deep vein thrombosis. The recent and well-publicized death of a British woman highlighted the dangers.

Simply getting up and walking around the cabin every few hours will help, but here's a simple exercise routine you can do right in your seat. The idea is to approximate taking a slow jog around a park. With simple, rhythmic movements, keeping your toes on the floor, alternately raise and lower each heel, rocking slowly from side to side, forward and back. Repeat 20 times.

Then imagine taking that same jog, but with your elbows pressed on your knees.

Step three: roll each shoulder forward and back in large circles. Next, exercise your neck. Turn your head slowly to look over each shoulder, then forward and back, and finally side to side.

Lay both arms along your thighs, palms down. Turn your hands over, spread your fingers, and make a fist. Relax and return to the original position.

Then tense your legs and stomach muscles, bend slightly forward, and try to raise your toes, keeping your heels on the ground.

Next, roll each foot in large circles to the fullest extent of your ankle's flexibility.

Finally, clasp your hands behind your neck and alternately and slowly raise each knee to touch the opposite elbow. Repeat this routine every few hours during a long flight, and you'll arrive with spring in your step, bounce in your back and color in your cheeks, both upper and lower.

One final caution: Before you get too far along in your exercise routine, it's always wise to let your seat mates know what you're doing.