An American Airlines pilot died suddenly during a red-eye flight early Monday, leaving the plane's first officer to make an emergency landing with 152 people on board. 

Early Tuesday, American Airlines formally identified the pilot as Captain Michael Johnston, 57. A statement from the airline said Johnson had broken into the commercial aviation industry as a first officer for America West Airlines in 1990. The statement did not specify how Johnston had died.

The Airbus 320 was en-route from Phoenix to Boston and had to be diverted to Syracuse. Before the flight landed there, the first officer called the airport tower and said "American 550. Medical emergency. Captain is incapacitated." 

The scenario is rare, but not unheard of. Seven pilots for U.S. airlines and one charter pilot have died during flights since 1994, according to the Federal Aviation Administration.

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

"[The crew] took extraordinary care of Mike, each other and our customers," the statement from American said. "We couldn't be more proud of the teamwork this crew showed during an extremely difficult time. Our airport teams in Syracuse and Boston were also instrumental in assisting our customers, and their handling is also greatly appreciated."

A replacement crew was sent to Syracuse, and the plane, an Airbus A320, landed in Boston at 12:30 p.m.147 passengers and five crew members were onboard.

"American 550. Medical emergency. Captain is incapacitated."

- First officer

Aviation experts said there was never any danger to passengers because pilots and co-pilots are equally capable of flying.

Ex-airline pilot John Cox, an aviation safety consultant, said when one pilot becomes unable to fly the other will rely on help from the plane's automated systems and get priority treatment from air traffic controllers.

"The passengers were not in danger, absolutely not," he said.

Passenger Louise Anderson, heading from Reno, Nevada, to Boston via Phoenix, told the Associated Press 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.

She said rumors of the pilot's death circulated in the Syracuse airport but were confirmed only by an announcement on their onward flight to Boston.

Anderson said the mood on board then was somber, but she commended the crew's handling of a tragic situation.

Airline pilots must pass physical exams every 12 months, every six months for captains 40 or older.

Captains and co-pilots usually take turns flying and doing takeoffs and landings, said former airline pilot James Record, who teaches aviation at Dowling College in Oakdale.

"The advantage to that is the co-pilot gets an equal amount of experience and the captain gets to see how the other guy flies," he said.

Record noted the co-pilot remained calm while describing the emergency and requesting permission from air traffic controllers to land.

"He was doing what he's trained to do — fly the plane," Record said. "He was probably more concerned with the health of his buddy, his crew member," than his ability to fly.

Modern airliners are capable of largely flying themselves. There's debate in aviation circles about whether over-reliance on automation is eroding pilots' flying skills. Incidents like Monday's help ensure regulators won't allow unmanned cockpits or unaccompanied pilots anytime soon.

The Associated Press contributed to this report.