A United Airlines pilot died after suffering a heart attack in the middle of a flight from Houston to Seattle on Thursday evening.

The 747 was forced to make an emergency landing in Boise, Idaho while two doctors on board the plane tried to perform CPR on the pilot, 63-year-old Capt. Henry Skillern. An off-duty pilot jumped into the cockpit to help the first officer land the plane.

"We got a man down, chest compressions going on right now," the aircraft’s first officer told air traffic controllers, reports CNN. "I'm not sure too much right now on status."

Skillern was still alive when the plane safely touched down and emergency responders came aboard the aircraft. He later died at a Boise hospital where he had been taken for treatment, reports CBS News.

According to the Houston Chronicle, Skillern had worked as a pilot for United Airlines for 26 years.

The 161 passengers on board the plane at the time of the emergency were all calm throughout the incident, according to Boise airport spokeswoman Patti Miller.

"It seemed like they felt that everything that could be done was being done," Miller said in a statement. "The passengers were concerned for him, but everyone was very calm."

Another pilot took over after the plane landed in Boise and flew the passengers to their original destination, according to CBS. They arrived safely in Seattle.