BOSTON (CBS) – A red-eye flight from Phoenix, Arizona to Boston was diverted to Syracuse Monday morning after one of the pilots suffered a medical emergency and died.

American Airlines Flight 550 left Phoenix Sky Harbor International Airport just before midnight and was scheduled to land at Logan Airport around 8 a.m.

A spokeswoman for the airline told WBZ-TV that one of the pilots became ill in mid-flight and the Airbus A320 was forced to land at Hancock Airport in Syracuse, New York just after 7 a.m.

KUTV has identified the pilot as Michael Johnston of West Jordan, Utah. His wife says she’s been told that her husband likely died of a heart attack.

In audio from the cockpit obtained by Live ATC.net, which provides live air traffic control broadcasts, the co-pilot is heard calling the control tower for “A medical emergency. Captain is incapacitated, request handling for runway one zero landing.”

Passengers, at first, were only told that the pilot was sick.

“The flight attendant came on and told us to fasten our seat belts…Her voice was quivering,” said passenger Peter McSwiggin. “So, I knew it was way beyond an illness.”

Most people on the plane didn’t know how serious the situation was until later.

“They put tarps up so we couldn’t see anything out of the windows. The cops evacuated everybody away from the windows,” said passenger Kelsey Harsh, “And then when we got here four hours later, they notified us that he passed away in the air.”

“We had to wait for the body to be removed from the plane,” said passenger Julia House. “It was pretty intense.”

Listen: American Flight 550 Co-Pilot Requests Help

The pilot died, the spokesperson said, but she would not say if he passed away during the flight or after it landed.

He was not taken to a hospital. There’s no word yet on a cause of death.

A replacement crew took over the flight in Syracuse and it left for Boston around 11 a.m.

The flight, which is also known as US Airways Flight 550, landed at Logan Airport at 12:30 p.m. There were 147 passengers on board.

Describing the incident to reporters in Boston, passengers said there was a quick descent, they felt some turbulence and then a member of the flight crew announced that the captain wasn’t feeling well.

The passengers described a hard landing in Syracuse and did not know at the time why they were there.

They said EMTs did not rush onto the plane, leading them to believe the pilot had died.

The passengers praised the co-pilot who they said appeared calm during the entire incident.

“Whatever happened in that cockpit, none of us will know, that co-pilot did a great job,” one passenger told WBZ NewsRadio 1030. “All of our lives were in his hands at that point.”

American Airlines flight #550 arriving at Logan after pilot died, diverted to Syracuse. Phoenix to Boston #wbz pic.twitter.com/uEVcqQUfKP — Christina Hager (@HagerWBZ) October 5, 2015

“This is a terribly sad event and American Airlines is focused on caring for the pilot’s family at this time,” the airline spokeswoman said, “as well as the American Airlines staff and passengers on board the flight.”

No other information is available at this point in the investigation.

WBZ-TV’s Christina Hager contributed to this report. You can follow her on Twitter @HagerWBZ.

WBZ NewsRadio 1030’s Bernice Corpuz reports: