It remains unclear what caused the pilot to pass out. Flight 473 was heading to Seattle Thursday when officials say the pilot lost consciousness somewhere over Oregon.
The co-pilot took over the plane and the Boeing 737-700 with 116 passengers and five crew members landed safely at Portland International Airport. The plane was met on the runway by emergency medical personnel and towed to the gate.
Airline spokesman Paul McElroy said the pilot was current on his six-month medical evaluation.
It's not clear if the passengers knew what was happening right away. As the news of the incident spread across the aircraft, passengers were pretty shaken up.
"I'm seeing the cockpit open completely and the pilot had come out, barged through the door, and fell on the aisle. He either passed out or had a stroke or something," described one passenger."Then the flight attendant was going up and down the aisle saying, 'Are there any paramedics, doctors, nurses, someone that can come and help?'"
The pilot, who was not identified, was taken to a hospital but there was no immediate word on his condition. McElroy says the pilot has been flying for Alaska for 28 years and the co-pilot is an 11-year Alaska Air veteran.
After the emergency landing, 20 passengers with connecting flights were put on a Horizon Air shuttle flight to Seattle on Thursday night. A new pilot was dispatched to Portland to fly the remaining passengers to Seattle on board the same plane.
This comes on the heels of an incident last month also involving an Alaska Airlines flight en route to Seattle. In that case, the co-pilot passed out, but the plane landed safely in Las Vegas.
The Associated Press contributed to this report.