Mystery surrounds an unknown illness which has spread though a passenger jet and forced it to turn round. Up to seven of 13 crew members and “many passengers” were struck down with the strange disease – but at this stage no one knows what it is. A British passenger has described panic on board the American Airlines flight from London Heathrow to LAX a when crew asked if there was a doctor on board.

A spokesman for the airline said there was “medical emergency” and people on the flight were “ill” but had no other information. Flight AA109 was close to Keflavik, a town in southwest Iceland, when crew declared a medical emergency and decided to head back to London. Passengers were asked if there was a doctor on board before the decision to abort the flight was taken at approximately 2.50pm. FULL REPORT