On 19 June 2009 a Boeing 767-300 being operated by Polish carrier LOT on a scheduled passenger flight from Chicago O’Hare to Warsaw was in the cruise at FL33033,000 feet 10.058 km in night IMC when one of the air speed indicators suddenly displayed a false high reading, which triggered an over speed warning. The flight crew response was based on the presumption that the speed increase was real and thrust was reduced and the aircraft put into a climb. A stall warning followed and descent was then made to a level 5000ft1,524 m below the previous cruise level followed by a diversion to Toronto. There were no injuries to the 216 occupants and the aircraft was undamaged.