The first officer of an American Airlines flight from Phoenix to Boston took over command of Flight 550 and safely landed the plane after the pilot became ill, officials said Monday.

The pilot died, according to the airline. It was unclear whether he died in the air or on the ground after the craft had landed in Syracuse, where it was diverted.

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

Flight 550 left Phoenix at 11:55 p.m. MDT Sunday and landed at 7:13 a.m. EDT, according to American Airlines spokesman Andrew Christie. The Airbus A320 carried 147 passengers and a crew of five, he said.

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

Details of the medical emergency and the identity of the deceased pilot weren't immediately released.

A replacement crew flew to Syracuse and continued the flight to Boston. The plane landed in Boston at 12:34 p.m. local time, Christie said.

Passenger Louise Anderson, who was heading from Reno to Boston via Phoenix, told The Associated Press that she had dozed off on the flight.

"What I woke up to was the flight attendant telling us we were making an emergency landing because the pilot was ill," she said.

The Federal Aviation Administration requires two crew members in the cockpit at all times for just such an emergency.