A United Airlines (NASDAQ: UAUA) flight from Houston to Seattle was forced to make an emergency landing at Boise Airport in Idaho after the captain suffered a fatal heart attack in mid-air.

According to ABCNews.com, Patti Miller, a spokeswoman for Boise Airport, confirmed that United Airlines Flight 1603 made the unscheduled landing at 8 p.m. on Thursday.

A passenger who was on the flight said that a crew member got on the loudspeaker and asked if there was a doctor on board, KOMONews.com reports.

“We got a man down, chest compressions going on right now. I’m not sure too much right now the status,” a crew member told air traffic control, according to ABCNews.com. “Can an ambulance and maybe some air stairs meet us on the runway?”

“The flight landed safely, and paramedics met the plane upon arrival and transported the crew member to the hospital," said Christen David, a spokeswoman for United.

According to the Guardian, the United Airlines pilot -- who has not been identified -- was transported to Saint Alphonsus Regional Medical Center in Boise, where he later died during the night while he was getting treatment.

“I am sad to confirm that our co-worker passed away last night,” David said. “Our thoughts are with his family at this time.”

The Boeing 737 had 161 passengers and six crew members on board.

Ken Martin, another passenger on the flight, told KOMONews.com that the woman sitting next to him was a first year resident doctor and attempted to perform CPR on the pilot. The pilot reportedly weighed 300 pounds and had to be moved to the first class cabin so they could perform CPR.

Despite the traumatic events, nobody panicked during the flight. "I'm really impressed with all the flight attendants," another passenger, Bryant Magill, told KOMONews.com. "They kept themselves calm. They kept it professional. There was no panic on the plane."

According to the Guardian, United Airlines eventually found another pilot and the plane landed at Sea-Tac Airport in Seattle at 12:07 a.m. PST on Friday morning.