United Airlines (UAL) has changed its policy for emotional support animals on its flights.

The policy change went into effect on Monday and limits emotional support animals from flying with the airline on flights longer than eight hours.

United Airlines said the decision was made because of a rise in onboard animal-related incidents,

The airline will also no longer allow kittens or puppies that are less than four months of age as support animals, in-cabin pets or service animals.

The company told WABC that animals that are typically this young haven’t had all the necessary vaccinations.

United isn’t alone with its support animal policy change as both Delta and Spirit have updated their policies to require at least 48 hours’ notice to bring a service animal aboard a flight.

As of this morning, United Airlines stock was down almost 1.5 percent.