The flight landed safely.
The plane was forced to make a detour due to a health issue with one of the crew.
Paul McElroy, an Alaska Airlines representative, said a pilot went unconscious, forcing the first officer to make an emergency landing at PDX.
The flight left LAX at 6:37 p.m. and was scheduled to arrive in Seattle at 9:30 p.m. There were 116 passengers and five crew members onboard the plane.
The pilot has been flying for Alaska for 28 years, and the first officer has been flying for Alaska for 11, according to McElroy.
The plane was met on the runway by emergency medical personnel. The plane was towed to the gate because the captain is the one who taxis to the gate.
Several passengers were booked on to a Horizon Shuttle to Seattle-Tacoma International Airport.
A flight crew was being flown in and the remaining passengers will be flown on the same plane. It was scheduled to take off around 12:30 a.m.
The plane is a Boeing 737-700.