Andrea Huguely said Flight 550 left Phoenix at 11:55 p.m. local time and was diverted mid-flight, landing shortly after 7 a.m. EDT. She said that after the flight's captain was stricken, the first officer safely landed the plane with 147 passengers and five crew members onboard.

"We are incredibly saddened by this event, and we are focused on caring for our pilot's family and colleagues," the airline statement said.

Details of the medical emergency and the identity of the deceased pilot weren't immediately released. It also wasn't clear when the pilot died.

Huguely said a replacement crew was sent to Syracuse and the plane later completed its trip to Boston.

Before the flight landed at Syracuse, the first officer called the airport tower and said in a calm voice, "American 550. Medical emergency. Captain is incapacitated." He requested a runway to land.

In a recording of his exchange with the tower, the officer expresses concern whether ambulance medics can get on the plane quickly. He's assured that they can, and is told to go into a gate where the medics would meet the plane.