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.