An American Airlines captain died at the controls mid-flight despite desperate attempts by an air stewardess to revive him.

The pilot of Flight 550, whose name has not been released, was flying from Phoenix to Boston on Monday morning when he became 'incapacitated'.

Taking control of the airbus, the first officer sent a panicked radio message to emergency ground control demanding permission to land as an air stewardess - a former nurse - fought to save his life.

Passengers told CBS News they felt a sharp drop and some turbulence before the co-pilot announced the captain was 'feeling unwell'.

The cause of death has not been released.

One passenger took to Twitter to explain what had happened on the American Airlines flight this morning

The plane carrying 147 passengers and a crew of five landed in Syracuse, New York, at 7.13am ET.

According to passengers, the EMTs did not appear to rush on to the airplane. Airlines cannot legally pronounce somebody dead in the air.

In a statement emailed to Daily Mail Online, an American Airlines spokesman said: 'Unfortunately, our captain passed away. We are incredibly saddened by this event, and we are focused on caring for his family and our colleagues.

'We also took care of our customers and sent a replacement crew to [Syracuse] to get them to Boston.

'They arrived safely and without incident at [approximately] 12.30pm local time in Boston.'

The plane departed Phoenix, Arizona, at 12.08am mountain standard time.

The moment the first officer radioed in the emergency can be heard in an audio recording first shared on savvystews.com.

'Medical emergency, captain is incapacitated, request handling for runway 108,' says the pilot.

After landing, a new crew was enlisted to fly the passengers to Boston's Logan Airport. They arrived shortly after 12.30pm local time.

American Airlines Flight 550 is believed to have been delayed by around four hours after the captain died mid-flight (file photo)

One passenger on board the flight took to Twitter to express her sadness at what had happened.

Louise Anderson, from Boston, said: 'The pilot died on our redeye back to Boston (leading to 4h in Syracuse). life is short. do what you love before it's too late.'