By Laura L. Myers

SEATTLE (Reuters) - A Seattle-bound Alaska Airlines flight made an emergency landing in Oregon after its veteran pilot passed out in the passenger cabin, in the second such fainting spell involving the U.S. carrier in 10 days, the airline said on Friday.

Flight crew and passengers helped revive the pilot and guide him into a vacant passenger seat while the co-pilot took control of the Boeing 737-700 and safely landed in Portland late on Thursday, airline spokesman Paul McElroy said.

"Doctors suspect he became ill due to food-poisoning or the flu virus," McElroy said of the pilot, a 28-year aviation veteran, adding that none of the 116 passengers and five crew members on board the flight from Los Angeles were injured.

The pilot was hospitalized in Portland, and McElroy said the two fainting episodes were a "bizarre coincidence."

Federal Aviation Administration spokesman Ian Gregor said investigators did not immediately see a connection between the incident and a similar situation on January 22 in which an Alaska Airlines co-pilot fainted on a flight between Seattle and Las Vegas, forcing the captain to make an emergency landing.

"That first officer was infected with the flu. We know that for sure," McElroy said.

(Reporting by Laura L. Myers, writing by Eric M. Johnson; editing by Cynthia Johnston, G Crosse)