Flight safety officials have revealed a spilled coffee caused a February transatlantic flight to turn around and land in Ireland.
The Air Accidents Investigation Branch (AIIB) said the hot drink damaged a cockpit audio control panel, resulting in smoke and a burning smell.
It said the damaged panel created “significant communication difficulty” for the pilots flying the Condor Airlines plane.
The captain could not receive or transmit messages and was unable to talk with the co-pilot, which resulted in a decision to turn back.
The Airbus A330 was over the North Atlantic Ocean on its way from Germany to Mexico and was diverted to Shannon in Ireland.
The pilots briefly used their oxygen masks and no one was injured in the incident.
The AIIB report said the captain had put his coffee on a tray table where objects were “vulnerable to being knocked over” against the advice of the plane’s manufacturer.
It said the airline used small coffee cups and as a result pilots were “generally discouraged” from using the official cup holders.
Condor has responded to the incident by ensuring cup lids are provided on all flights and by supplying larger cups.
The Civil Aviation Authority said diversions typically cost between £10,000 and £80,000 depending on the size of the aircraft and where it lands.