The cat's carrier must be able to fit under the seat and the bottom should be lined with an absorbent material in case of accidents. ("Puppy pads" are made of the same material as disposable diapers and are excellent for this purpose.) Be prepared to present a veterinarian-signed health certificate dated no more than ten days before the scheduled flight. If the cat is riding with you, let the person sitting next to you know that you have a cat, just in case they have allergies or phobias.

   If your cat cannot travel in the cabin with you, it will ride in the baggage hold. Although this compartment is pressurized and the extremes of temperature are regulated, it's still a good idea to travel during the coolest part of the day if you're travelling in the summer (the early morning or late evening). Choose a non-stop flight and request that your cat be hand-carried to and from the plane. Make sure your USDA-approved shipping crate is marked with contact persons at both the departure and arrival sites and has sturdy handles that won't come off during handling. Make sure all the bolts securing the halves of the carrier are in place and tightened. Your pet should be wearing an identification tag on an elastic collar.

   If the trip is longer than six hours, you will want to have dry food and ice cubes in untippable dishes in the carrier. Be sure to talk directly to the freight handling personnel at the airport. Make the staff check and report back. (Most pet fatalities occur on the ground, when animals are left in their crates on the hot tarmac or in stifling cargo holds.)

   Be aware that there are regulations regarding the range of temperatures when a pet may be shipped. If the temperature on the ground in your departing, connecting, or arriving city falls outside these limits, you may run into unexpected delays or cancellations. It's also wise to avoid peak travel times around holidays when air traffic is heaviest so your cat can get more personal attention.

   A few additional tips:

   - It is generally better not to have your cat tranquilized before flying. The combination of high altitude and limited oxygen is a challenge your pet's body is better prepared to meet if he is not sedated.

   - Talk to a supervisor when you get to the airport and tell him you have an extremely valuable pet in terms of dollars, even if it's a mixed breed. Otherwise, experts indicate, some baggage handlers couldn't care if you were carrying a rock.

   - Personalize your cat to the handlers. Put signs on the crate saying, "Hi! I am a Persian kitten. This is my first trip. Please handle my crate carefully."

   - When you board a plane, tell the pilot that you have a cat in the hold worth a great deal of money, even if it isn't. Also, tell them to make sure to turn on the heat and pressurization in the cargo compartment (this is done from the cockpit and someone may have forgotten to give the pilot that information). Cargo compartments can get as hot as 140 degrees, and intense cold can be just as damaging to your cat.

   - Put large strips of red or orange fluorescent material all over the crate so you can spot it from a long ways across the airport and your cat won't get mixed up with anything else. Put arrows or the words "Top" and "Live Animal" on top of the crate so your cat doesn't fly upside down.

   - Put your home addresses and phone numbers, plus those of where you're going, inside and outside the crate, because many people won't reach into a kennel for fear of being scratched or bitten.

   - Watch the ticket clerk attach the destination tags at the airport.

   - Make certain your pet is loaded last, especially during extreme weather conditions. This may also ensure that he is taken off the plane first.

   - Ask the airline if you can watch your cat being loaded and unloaded at the cargo hold.

   Of course, in addition to federal regulations, each airline has its own regulations, so it's absolutely imperitive that you check the individual air carrier's rules before booking a flight for you and your cat. The Air Transport Association has a free booklet, Air Travel for Your Dog or Cat, available by sending a self-addressed, stamped, business-sized envelope to: ATA, 1301 Pennsylvania Blvd. N.W., Suite 1100, Washington, D.C. 20004.