If you travel on Delta Air Lines ( DAL ), there will be fewer animals as your fellow passengers.
The second-largest airline in the U.S. is updating its policies on service and emotional support animals on flights. Starting Dec. 18, 2018 – right before peak holiday travel – service and support animals under four months old are not allowed on any flight, Delta announced Monday.
The rule is stricter next year. Effective Feb. 1, 2019, emotional support animals can’t board flights longer than eight hours.
Most domestic flights are less than eight hours, so passengers flying with emotional support animals internationally are more likely to be affected.
Delta said its decision stemmed from an 84% increase in reported incidents involving service and support animals from 2016 to 2017 on its flights. Incidents include a support dog that attacked a man who ended up needing 28 stitches last year. Currently, the airline carries 700 service animals daily, or 250,000 every year.
This is the third time this year that Delta Air Lines has tightened its policy on service animals. In January, it announced new procedures and updated requirements for customers traveling with service and support animals. It also prohibited all “pit bull-type dogs” as service or support animals in June as “the direct result of growing safety concerns following recent incidents in which several employees were bitten.”
The airline says its policy is in line with CDC vaccination requirements and the Air Carrier Access Act (ACAA), which states airlines may exclude animals that “pose a direct threat to the health or safety of others” or “cause a significant disruption of cabin service.” But the Department of Transportation has questioned its previous policy, saying “a limitation based exclusively on breed of the service animal is not allowed under the Department’s Air Carrier Access Act regulation” in a statement.
Airlines have been tightening policies on service and emotional-support animals allowed to fly with passengers, including untrained pets and unusual species. United Airlines updated its rules after a woman tried to bring a peacock with her on a flight. American Airlines requires passengers to notify the carrier about a comfort animal 48 hours before a flight, and have a letter stating the need for the animal.
Note: The headline has been updated to reflect only emotional support animals have been banned on long flights.
Krystal Hu covers technology and trade for Yahoo Finance. Follow her on Twitter .