(CNN) -- British Airways confirmed the emergency landing of an A321 last month after the pilots complained of feeling lightheaded and put on their own oxygen masks.
The flight bound for Glasgow, Scotland, on December 20 returned to London's Heathrow Airport shortly after takeoff, said airline spokesman Richard Goodfellow. Airline engineers checked the aircraft after landing and dismissed the possibility of contaminated air in the cockpit, Goodfellow said.
He would not comment on the cause of the incident while an national investigation is ongoing but said, "We believe it was an isolated incident."
Reports of the incident surfaced over the weekend in the British press after passengers apparently posted details on a flight-oriented website.
A senior flight attendant was called to the flight deck about 20 minutes after takeoff and alerted by the pilots that they were using their emergency oxygen supply, Goodfellow said, disputing reports that the pilots needed flight attendant assistance to put on the oxygen.
"The pilots followed the flight procedures they were highly trained for, and the flight landed without incident," he said.
After a safe landing, the 116 passengers were placed on a new flight with an entirely new crew, he said. The pilots were examined by an airline doctor but were not hospitalized. The plane was returned to service.