Attempts to tell Heathrow airport's sleeping chief executive that the airport had been closed because of a power outage failed because his bedside phone was on silent, an inquiry has found.
Thomas Woldbye was in bed as senior Heathrow staff decided to suspend operations because of a fire at a nearby electrical substation.
No flights operated at the west London airport until about 18:00 GMT on 21 March because of the blaze which started late the previous night.
The closure, which affected 270,000 journeys, was caused by "an unprecedented set of circumstances", Heathrow chairman Lord Deighton said, adding the airport's infrastructure will be made "more fit for the future".