PITTSBURGH — A dog accompanying an elderly New Jersey woman on a US Airways flight to Phoenix became agitated and bit a passenger and a flight attendant today, forcing the pilot to make an unexpected stop in Pittsburgh.

The 12-pound Manchester terrier named Mandy was riding in an approved carrier on Flight 522 from Newark, N.J., airline and local authorities said. The dog’s 89-year-old owner was one of 122 passengers and five crew members aboard.

The dog bit a passenger who had tried to calm it and then broke out of its cage, officials said. The animal then ran up the plane’s aisle and bit a flight attendant who tried to grab it.

The bites were not severe, but the pilot landed the plane as a precaution, US Airways spokesman Todd Lehmacher said.

“We allow pets in the cabin as long as they are in an approved container and under the seat in the carrier,” Lehmacher said.

The flight resumed without the woman and her dog, and landed in Phoenix hours later. The woman, whose name was not released, spoke with authorities in Pittsburgh before boarding a different flight to Phoenix with her dog.