A dog is seen on the lap of its owner in a plane in Chiba, Japan on January 27, 2017.

Delta Air Lines plans to ban emotional-support animals from flights longer than eight hours and will bar all service and support animals under four months old starting this month.

It is the airline's latest attempt to curb the surge in passengers flying with service and support animals, which Delta has said has led to soiled cabins and biting. In June 2017, a passenger's emotional-support dog bit the face of another traveler.

The changes apply to Delta tickets purchased on or after Dec. 18, the company said Monday. Starting Feb. 1, 2019, no support animals will be allowed on board flights longer than eight hours and service and support animals under four months of age, such as puppies, won't be allowed on any Delta flight.

"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," said John Laughter, Delta's senior vice president for safety, security and compliance. The number of incidents involving support and service animals on board increased 84 percent between 2016 and 2017, Delta said.

Support and service animals fly free of charge and without a carrier under the 1986 Air Carrier Access Act. But passengers and crew members have complained about allergies, animal aggression, including biting, and soiled cabins from the increase in support animals, leading airlines to issue their own restrictions.

All major U.S. airlines have tightened rules for emotional-support animals on board this year, requiring written confirmation that the animals are trained, amid complaints from passengers and crew members. Some airlines, including JetBlue Airways, have limited the types of support animals that they'll allow on board to cats, dogs and miniature horses.

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