Delta Airlines is banning service and comfort animals on their long-haul flights.

Starting on February 1, comfort or emotional support animals will not be allowed on flights over eight hours long, staying in code with the principles of the U.S. Department of Transportation’s Air Carrier Access Act. Going along with the vaccination policy of the U.S. Centers for Disease Control, animals younger than 4-months-old also will not be allowed on any flight, regardless of the duration.

The new regulations come after numerous incidents with animals on flights this year, increasing 84 percent since 2017. Flying close to 700 service animals per day, Delta reported one attack involving a 70-pound dog. Other incidents include animals biting and defecating on planes. The airline first started to crack down on animals back in July, allowing one animal per passenger and no longer accepting pit bulls or “aggressive breeds” as service or support animals. “We will continue to review and enhance our policies and procedures as health and safety are core values at Delta,” Senior VP of Corporate Safety John Laughter said.

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“These updates support Delta’s commitment to safety and also protect the rights of customers with documented needs such as veterans with disabilities to travel with trained service and support animals,” he continued. The changes won’t effect tickets purchased before December 18. Delta passengers who have already requested permission to travel with service or support animals will be allowed to do so if their ticket was purchased before that date.

Other airlines like United, American, JetBlue, and Southwest have already announced new restrictions regarding animals. Passengers were starting to bring all types of animals on board like turkeys, goats, snakes, and even pigs. Animals as such have been completely banned with others needing additional documentation. Delta’s current policy says all support and service animals must be trained to behave in public and are required to stay by their owners at all times.

Any animal that shows aggressive behavior could be denied boarding.