According to report, a strange incident occurred on American Airlines Flight AA109 from London to Los Angeles where 6 cabin crew members and two passengers suddenly fell ill, forcing the plane to declare an emergency landing and return to London.
When they landed at Heathrow, passengers said they were not told anything other than they should remain in their seats. An official from the London Fire service got on board the plane to carry out tests on the air inside the cabin before passengers were allowed to disembark but their luggage was confiscated for analysis. Panicked passengers told of the moment a plea went out for any doctors on-board the American Airlines flight, before the captain declared a 'medical emergency' and returned to London.
Source: UK Daily Mail