Alaska Airlines apologized this week after a flight attendant asked a gay man to give up his seat next to his partner so a straight couple could sit together, an exchange that put the airline on the defensive as it rebutted claims of discrimination.

David Cooley, the owner of a gay bar in West Hollywood called the Abbey, wrote on Facebook on Sunday that he and his partner had boarded a flight to Los Angeles from New York when a flight attendant asked if Mr. Cooley’s partner would move from his seat “so a couple could sit together.”

Mr. Cooley said he told the attendant that the two men were a couple and that he wanted to sit with his partner. But the attendant gave Mr. Cooley’s partner a choice: Move for the other couple or get off the plane.

“We could not bear the feeling of humiliation for an entire cross-country flight and left the plane,” Mr. Cooley said. “I cannot believe that an airline in this day and age would give a straight couple preferential treatment over a gay couple and go so far as to ask us to leave.”