“Support animals” will no longer be allowed on United Airlines flights longer than eight hours.

United officials say they are seeing more on-board animal-related incidents, adding many are not used to spending so much time on a plane.

In addition, United won’t allow kittens or puppies less than four months old as support animals, in-cabin pets, or service animals. The airline says animals that young typically haven’t had all necessary vaccinations.

United joins Delta Airlines in changing polices on emotional support animals.