The captain was removed from flying duties after a series of sordid images seemingly shot in a Boeing 777 on a long-haul flight emerged, the Sun reports.
Other images show a pornographic magazine spread on the controls and explicit playing cards scattered around the cockpit.
Serial numbers on the control panel suggest the pictures were taken aboard at least two separate British Airways planes.
The airline confirmed on Saturday it was probing the images — and whether they were taken mid-flight.
BA said: “We are taking these allegations extremely seriously.”
The captain in question is thought to have denied to bosses the pictures are of him.
A senior airline source said investigators would examine whether the images could have been shot in a flight simulator, the Sun reports.