Q: On a recent flight, a passenger behind my wife had a cat in a cage under the seat. The meows were not as bad as the defecation, which came after the plane was airborne. I later called both US Airways and United, whose agents told me, in effect, that if I were bothered by an animal, it was just too bad. Is that accurate?

John Gehrs

Virginia Beach

A: I asked Terry Trippler, an expert on airline regulations and author of "Rules of the Air," to comment on your wife's dilemma. "As usual, the airline agents don't even know their own rules," he said. Trippler accurately pointed out that both United and US Airways, and most major airlines, have rules requiring that an animal being transported in the passenger cabin "must be harmless, inoffensive, odorless and require no attention during transit."

United's rule does not discuss what happens if the pet doesn't read the fine print, but US Airways' Rule 200 says, "In the event the animal becomes offensive, or causes a disturbance during transit, the pet will be removed at the first enroute stop, and placed in the cargo compartment of the aircraft."

David Castelveter, spokesman for US Airways, said that theoretically, if an animal becomes "an absolute inconvenience or nuisance, the captain could land the plane at the nearest airport and have the pet moved to the cargo area." Practically, however, this is highly unlikely; Castelveter said he has never heard of it occurring. "We would move the pet within the plane so as not to bother the passengers," he said.

Chances are that if your wife had complained vigorously enough, either she or the pet probably would have been moved. As for why the pet owner didn't clean up the mess, the FAA mandates that pet crates not be opened while a plane is in flight. (Just imagine if the temporarily pyschotic animal had escaped during the cleanup.)

Q: My four-year-old is fascinated by the desert. Where can we can introduce him to a variety of desert environments?

Louise Sperling

Arlington

A: You could introduce your son to four different types of desert within Arizona alone.

Arizona is dominated by the Sonoran Desert, but the Chihuahuan, the Mojave and the Great Basin all extend into this Southwest state.

The Chihuahuan Desert is situated mostly in New Mexico, but extends into extreme southeastern Arizona. With elevations between 3,500 and 5,000 feet, it is a land of extremes; winters are long and cold, and summers are blistering.

The Sonoran Desert, a low-lying desert with elevations under 3,000 feet, is the most botanically diverse of the North American deserts.

The Mojave Desert, which spills into Arizona from California, gets very little rain, creating a gaudy display of wildflowers in early spring.

Arizona's northwestern corner holds the Great Basin Desert. At elevations higher than 4,000 feet, the Great Basin is not as botanically diverse and is dominated by sagebrush.

If your child were older, I'd advise doing the grand tour. But with a 4-year-old, you'll be better off staying in one place. Stay in the desert outside Tucson at either a bed-and-breakfast or a guest ranch. Choices include Casa Tierra (520-578-3058), a bed-and-breakfast on five acres in the Sonoran Desert about 30 minutes west of Tucson; Hacienda del Desierto (1-800-982-1795, www.tucson-bed-breakfast.com), a bed-and-breakfast adjacent to the Saguaro National Park East; La Tierra Linda Guest Ranch Resort (1-888-872-6241, www.latierralinda .com), a 30-acre-ranch adjacent to Saguaro National Park West; and the Lazy K Bar Guest Ranch (1-800-321-7018, www.lazykbar.com), about 14 miles northwest of Tucson.

Within driving distance of Tucson, there are many desert-related sites. The Saguaro National Park, divided into two sections on either side of Tucson, showcases large stands of giant saguaro cactus. The eastern section, with elevations of up to 7,000 feet, includes high desert habitats and an easily walked Desert Ecology Nature Trail.

The western section, with much lower elevations, has a six-mile loop road that passes through cactus forests. Information: 520-733-5153, www.nps.gov/sagu. The Arizona-Sonora Desert Museum (520-883-1380, www.desertmuseum.org) is a combination zoo, natural history museum and botanical garden. It has a wide variety of specialized family programs designed for older children.

For a detailed tourist guide, contact the Tucson Convention and Visitors Bureau, 1-800-638-8350.

Q: We would like to do a three- to five-day trek in Tibet, preferably from Lhasa, perhaps from Ganden to Samye. We would like a trekking company to arrange the details, equipment and a guide, but we would like not to be in a group.

Tom Lee

Washington

A: Arranging travel to Tibet is complicated for individual travelers. Demand, however, is high. Many companies offer both group trips and customized tours to this out-of-the-way destination. Several good companies to contact:

* Mountain Journeys (1-888-299-5005, www .mountainjourneys.com), a Wyoming-based tour group, will arrange custom tours to Tibet. It also offers a 20-day Tibet tour that includes a five-day trek between the Ganden and Samye monasteries; cost is about $3,150 per person plus air fare.

* Himalayan Travel (1-800-225-2380, www .gorp.com/himtravel.htm), based in Connecticut, has been offering trips to Nepal and Tibet for more than 20 years. It will customize a tour and also offers an eight-day "Tibet Overland Expedition" from Lhasa across the Tibet Plateau to Nepal; cost is about $1,300 per person plus air fare.

* Mountain Travel Sobek (1-888-687-6235, www.mtsobek.com) is a luxury tour company that offers an 18-day tour of Nepal and Tibet, which includes seven days of trekking in Tibet. Cost is about $5,400 plus air fare from the United States.

A good source of general information is the Tibet Tourism Bureau. Its Web site, www.tibet-tour.com, explains how to obtain the coveted "Alien's Travel Permit," which, in addition to the basic Chinese visa, must be procured before entering Tibet. If you can manage to get the permit and make your way to Lhasa, you will be able to find a guide through your hotel. Recommended hotels in Lhasa include the Yak, Snowlands and Kirey.

Send queries by e-mail (travelqa@ washpost.com), fax (202-334-1069) or U.S. mail (Travel Q&A, Washington Post Travel Section, 1150 15th St. NW, Washington, D.C. 20071).