A pilot and a flight attendant were dismissed from Cathay Pacific after photos of them having oral sex in a cockpit appeared online and in print, the Hong Kong airline said.
The airline's chief executive John Slosar said the couple, who have not been identified, "are no longer employees of the company."
He stressed that the incident did not happen while a plane was airborne and said a report would be forwarded to Hong Kong's Civil Aviation Department.
"I find any behaviour that recklessly soils the reputation of our company or our team members as totally unacceptable," Slosar said.
"That's why we moved as swiftly as we could to ascertain the facts of the case, and to take decisive action."
According to Chinese newspaper reports, the pilot protested that he and the flight attendant are a couple and that the pictures were downloaded from his personal computer without his knowledge.