For many pet lovers, a vacation wouldn't be complete without their dog or cat beside them.

But taking a pet on a plane can be tricky. Negotiating the maze of travel restrictions, which vary widely from airline to airline, is daunting. Many carriers allow small dogs or cats to ride under the seat in front of you; others don't. Some will take a large dog in the cargo hold in a kennel. Other airlines won't allow pets, period.

It's especially important to check the rules if you're traveling in the summer or winter, when many airlines have restrictions because of extreme temperatures. In the summer, some airlines prohibit pet travel to cities where the temperatures are really hot, such as Las Vegas. Sitting on the tarmac in a kennel when it's boiling hot can kill a pet.

Here's a rundown of some of the major airlines and their current policies. This information applies only to pets, not to certified service animals, such as seeing-eye dogs, because airlines are required to follow government regulations on travel for such animals.

Once you select an airline, remember to check the rules on vaccinations and a pet's health status, which can differ from state to state. International guidelines are even more complex.

ALASKA AIRLINES

Pets in cabin: Dogs, cats, rabbits and household birds.

Pets as luggage: Alaska and Horizon Air accept most small domesticated pets in the climate-controlled luggage compartment. Other pets may be accepted with approval. Pets accepted include dogs, cats, ferrets, hamsters, guinea pigs, pot-bellied pigs and nonpoisonous reptiles.

Cost: $75 each way in the cabin. In cargo, it's $100 each way for a pet and kennel weighing up to 149 pounds combined.

Limit: One per traveler.

How many pets per flight: In the cabin, one in first class and five in the main cabin, for a total of six per flight.

Booking your pet: Call (800) 252-7522 in advance.

Carrier restrictions: In the cabin, the carrier must fit under the seat, and the pet must be able to move comfortably. Dimensions vary. See the website, or call reservations for specifics. In the climate-controlled luggage compartment, the largest kennel Alaska will accept is what is known as a 500-size.

Carrier availability: A limited number of in-cabin carriers are for sale at most airport locations. Please arrange in advance.

Special restrictions: If the temperature is too hot or too cold, the airline may not take pets in the cargo hold. Animals with offensive odors or those that are noisy must travel in the hold.

Perks: Once a pet is loaded into the luggage compartment, a ticket confirming the animal is onboard is delivered to the traveler.

AMERICAN AIRLINES

Pets in cabin: Cats and dogs only, 20-pound limit.

Pets checked as luggage: Two pets and two kennels are allowed per passenger, with each pet in a kennel; there are some exceptions (contact the airline). The maximum weight with a kennel is 100 pounds.

Cost: Cabin pets, $80 each way. As checked baggage, $100 each way.

Limit: See above.

Maximum pets per flight: Seven.

Booking your pet: Call reservations in advance, (800) 433-7300.

Carrier restrictions: Soft-sided carriers OK, as long as they are made of nylon and have ventilation. Can't weigh more than 20 pounds.

Carrier availability: None.

Special restrictions: Check with reservations agent for hot and cold temperature restrictions. Will refuse animals exhibiting aggressive behavior. Special restrictions for travel to Hawaii.

Perks: None.

CONTINENTAL AIRLINES

Pets in cabin: Cats, dogs, rabbits and small birds.

Pets checked as luggage: Not allowed. But the airline's PetSafe cargo program accommodates all sizes of kennels for pets weighing up to 250 pounds. Call the 24-hour live-animal desk at (800) 575-3335. You can also track your animal's journey online through the PetSafe program at www.cocargo.com.

Cost: $95 each way in the cabin. Check for cargo rates.

Limit: One pet per traveler.

Weight: No limit, but pets must be in a carrier that can fit under the seat.

Maximum pets per flight: Four pets in economy class and one in first class. (No pets in the BusinessFirst cabins. )

Booking your pet: For in-cabin pets, book online or call Continental reservations, (800) 525-0280.

Carrier restrictions: The carrier must fit under the seat.

Carrier availability: In-cabin pet kennels are available at some airports for $55.

Special restrictions: No pets in the cabin to and from Hawaii. No American pit bulls anywhere, unless they are puppies ages 8 weeks to 6 months and don't weigh more than 20 pounds. Also, no pets are shipped if they have been sedated. This is due to a recommendation from the American Veterinary Medical Assn.

Perks: The airline has one of the industry's most extensive programs for pets. Continental also operates a kennel in its cargo area at George Bush Intercontinental Airport in Houston, the nation's only such facility. Overnight kenneling and grooming services are available. The airline also provides personal handling in climate-controlled vehicles for connections between flights when temperatures rise. Your pet can also earn frequent-flier miles.

DELTA AIR LINES

Pets in cabin: Dogs, cats, birds, ferrets, rabbits, hamsters and guinea pigs.

Pets as checked luggage: Because of heat concerns, pets cannot travel from May 15 to Sept. 15. During other times, only warm-blooded mammals and birds considered to be pets or show animals are allowed. Two kennels are allowed per flight.

Cost: In-cabin fee is $50. Pets checked as baggage are $100.

Limit: Only one carry-on pet per passenger. Two pets are allowed in cargo.

Maximum pets per flight: Two in the main cabin.

Booking your pet: Call (800) 221-1212.

Carrier restrictions: The carrier must fit under the seat.

Carrier availability: None.

Special restrictions: Animals must be "non-offensive" and not pose a danger to passengers or baggage handlers.

Perks: The Delta Pet First service is intended to ensure animal safety and comfort. The airline has temperature-controlled live-animal holding areas in its four hub cities: Atlanta, Cincinnati, Dallas and Salt Lake City.

JETBLUE

Pets in cabin: Small dogs and cats.

Pets in cargo: Not allowed, because of a lack of oxygen and pressurized air.

Cost: $50 each way.

Limit: One pet per traveler.

Weight: The combined weight of the pet and carrier can't exceed 20 pounds.

Maximum pets per flight: Four.

Booking your pet: Customers must call reservations and let them know they are traveling with a pet. Cannot use online flight check-in. (800) 538-2583.

Carrier restrictions: Must fit under the seat and have a leak-proof bottom.

Carriers availability: Soft-sided carriers that are 3 1/2 pounds empty are available for $60 (nonrefundable).

Special restrictions: No cargo pets.

Perks: TrueBlue travelers with pets earn double JetBlue miles.

NORTHWEST

Pets in cabin: Dogs, cats and household birds.

Pets as checked baggage: Allowed. Dogs, cats, household birds and other pets such as rabbits and hamsters can travel with your luggage on domestic flights; advance arrangements are required, and the airline recommends you choose nonstop flights. Only dogs and cats can travel with luggage on international flights.

Cost: $80 each way in the cabin. For pets traveling with luggage, the cost is from $139 for small pets to $359 for animals weighing 150 pounds or more.

How many: One per traveler.

Maximum pets per flight: Six carry-on pets per flight.

Booking your pet: For carry-on pets, call Northwest reservations and pay fees in advance. For checked pets, check the website before calling, www.nwa.com, or call (800) 225-2525.

Carrier restrictions: Combined weight of carry-on kennel and pet not more than 15 pounds. Carriers must be leak-proof and ventilated on two sides.

Carrier availability: None.

Restrictions: Because of heat, embargo from June 1 through Sept. 15 for pets traveling to Las Vegas and all cities in Alabama, Arizona, Arkansas, Florida, Louisiana, Mississippi and Texas.

Perks: Offers the Priority Pet Program, with employee training at all locations and transportation in heated and pressurized luggage compartments. Also offers a more costly same-day shipping service for pets traveling in cargo.

SOUTHWEST

Pets: No pets allowed.

UNITED AIRLINES

Pets in cabin: Dogs, cats and household birds.

Pets as checked baggage: Cats, dogs and household birds. For other animals, contact United Cargo at www.unitedcargo.com

Cost: Cabin pets cost $85 each way; in cargo, it's $100 for smaller pets and $200 for medium-size to extra-large pets.

Limit: One pet per traveler.

Maximum pets per flight: Depends on the aircraft. Check with the airline.

Booking your pet: Call (800) 864-8331. Special cold- or hot-weather restrictions may apply for those traveling in the cargo area, so reconfirm your trip 24 to 48 hours before the flight.

Carrier restrictions: It must fit under the seat.

Carrier availability: Carriers are available.

Restrictions: Short-nosed dog breeds such as Boston terriers, boxers and English bulldogs are not accepted as cargo or checked baggage during the hotter months, June 1 to Sept. 30. Tropical birds such as parrots are not accepted in the cabin.

Perks: None.

US AIRWAYS

Pets in cabin: Small dogs, cats or birds.

Pets checked with baggage: Not allowed; hub cities of Phoenix and Las Vegas have extreme temperatures. The only exception: On nonstop shuttle flights to Boston, New York and Washington, D.C., some pets are accepted as checked baggage. The customer must be on the same flight.

Cost: $80 each way.

How many: One per passenger.

Maximum pets per flight: The number of pets in the cabin is limited. Check with the airline.

Booking your pet: Call (800) 428-4322 to coordinate your pet travel plans.

Carrier restrictions: Hard-sided carriers up to 17 inches long and 16 inches wide are allowed, as well as soft-sided carriers that are leak- and escape-proof.

Carrier availability: None.

Special restrictions: Pets are not allowed in the cabin for travel to and from Hawaii.

Perks: None.


Email us your comments and feedback