A United Airlines captain suffered an apparent heart attack while piloting a plane from Houston to Seattle and passengers stepped in to help with a doctor performing CPR and an off-duty pilot assisting in the emergency landing in Idaho.

The captain was still alive when he arrived at Saint Alphonsus Regional Medical Centre but died overnight while undergoing treatment, spokeswoman Jennifer Krajnik said.

A Boise airport spokeswoman said that the man suffered an apparent heart attack.

The cause of death has not been announced. There were 161 passengers on board.

Passenger Ken Martin told Seattle TV station KOMO a first-year resident doctor sitting next to him volunteered to help perform CPR. She told Martin the pilot appeared to weigh over 136 kilos and was taken into the first class cabin where CPR was performed.

Passenger Bryant Magill described a calm scene onboard.

“I’m really impressed with all the flight attendants,” Mr Magill told KOMO.

“They kept themselves calm. They kept it professional. There was no panic on the plane.”

The airline did not give the pilot’s name, citing privacy reasons. “I am sad to confirm that our co-worker passed away last night. Our thoughts are with his family at this time,” spokeswoman Christen David said in an e-mail.

Another off-duty United pilot was onboard and helped land the plane.

Pilots are required to get medical certificates that show they don’t have major heart problems, according to the Federal Aviation Administration website.

United flight 1603 from Houston to Seattle diverted to Boise for the medical emergency.

The flight landed safely and was met by paramedics who took the pilot to the hospital.

The Boeing 737-900 had 161 passengers and a crew of six. Another pilot flew the original plane and passengers to Sea-Tac Airport.

Officials later identified the United Airlines captain who died after suffering a mid-flight heart attack as 63-year-old Henry Skillern of Humble, Texas.

Ada County Coroner Erwin Sonnenberg performed an autopsy on Skillern late on Friday morning and confirmed that he died at a Boise hospital of a heart attack.

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