A Polish flight was grounded at Heathrow after a random check found both of its pilots to be too old.
The LOT flight from London to Warsaw was refused permission to fly after the British Civil Aviation Authority found that both pilots were over 60.
In 2006, the International Civil Aviation Authority ruled that at least one of the flight crew be under 60. The maximum age for a pilot is 65.
According to the Mirror, the 70 passengers on board had to wait five hours while a replacement pilot was flown in from Poland.
The Polish airline told the Daily Telegraph: "LOT knows the rules and strictly adheres to them. But in this case there was an unfortunate coincidence.
"The crew roster was completed shortly before the aircraft left Warsaw, and the crew scheduling system did not issue a warning that both pilots were over 60, which it always does."
The flight was due to leave at 10.35am and eventually took off at 15.35pm.
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