Delta Air Lines says for safety reasons it will require owners to provide more information before their animal can fly in the passenger cabin, including an assurance that it's trained to behave itself.
The airline says complaints about animals biting or relieving themselves have nearly doubled since 2016.
Starting March 1, Delta will require owners to show proof of their animal's health or vaccinations at least 48 hours before a flight. Owners of psychiatric service animals and so-called emotional-support animals will need to sign a statement vouching that their animal can behave. But owners will be on the honor system: They won't have to show, for example, that their dog graduated from obedience school.
Delta's policy change arrives with the number of animals in the cabin increasing.
John Laughter, the airline's senior vice president of safety and security, said there are insufficient rules in place to screen animals for health and behavior issues. He said Delta sought a balance "that supports those customers with a legitimate need for these animals" while maintaining safety.
Delta's new rules are aimed at two categories: service animals, which receive specific training to help blind or disabled passengers; and so-called emotional-support animals, which require no training at all. Both fly for free and are not required to be caged during the flight.
The emotional-support group has been growing rapidly and is the target of most of the new Delta procedures.