Airlines didn't always let pets fly. Gayle Martz, a former flight attendant, persuaded airlines to change pet travel rules.

"I knew the anxiety that people went through (when they) wanted to take their pets with them," she said.

Martz designed the "sherpa bag," a soft alternative to hard kennels that is approved as a carry-on.

"Sherpa bags all conform to the underneath-the-seat dimensions on an airplane, so the animal can have more room. They've got mesh panels for ventilation," she said. "It's lightweight. It gives them a private den that they can travel in where they're safe and secure."

Pet owners also should remember that the weather can complicate matters. Last summer, United and Delta banned pet travel in cargo because of extreme heat. American and Northwest restrict pet travel in cargo when the temperature climbs above 85 degrees or falls below 45 degrees.