As the trend toward restricting emotional support animals continues, United is the latest airline to make it harder for passengers to travel with pets. Last week, United announced that it will ban all emotional support cats and dogs under four months old. This follows the same decision by Delta last month, banning puppies and kittens under four months old. United’s other rule change also follows in Delta’s footsteps, banning all emotional support animals on flights longer than eight hours. The policy goes into effect immediately, beginning today.

In an emailed statement, United said, “We have seen increases in onboard incidents on longer flights involving these animals, many of which are unaccustomed to spending an extended amount of time in the cabin of an aircraft.”

This isn’t the first step United has taken toward placing restrictions on emotional support animals. In March 2018, it began requiring a health and vaccination form, signed by the pet’s veterinarian, to confirm that “the animal has been trained to behave properly in a public setting.” For emotional support animals over 4 years old, on flights under eight hours, that rule is still in effect. United also needs 48-hour notice and a letter from a mental health professional before passengers will be allowed to fly with an emotional support animal.

The rule change only applies to passengers who made reservations after January 3, 2019. Those who purchased tickets prior to this date will still be allowed to fly with emotional support animals, according to the old rules.

H/T: Condé Nast Traveler