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".
Heathrow commissioned the inquiry into what happened, led by former transport secretary Ruth Kelly, who is an independent member of the airport's board.
The Kelly Review found that Mr Woldbye "was not involved" in the decision taken by the airport's chief operating officer Javier Echave at 01:15 on 21 March to suspend operations until 23:59.
Alerts known as F24 alarms were sent to Mr Woldbye's mobile at 00:21 and 01:52 to activate emergency procedures, and Mr Echave tried to call him several times.
The report stated: "Mr Woldbye first became aware of the incident at approximately 06:45 on 21 March, and received a debrief from Mr Echave."
Mr Woldbye expressed "his deep regret at not being contactable during the night of the incident", the review said.
The review recommended that Heathrow considers having a "second means of contact" to notify key individuals about critical incidents.
The Sunday Times first reported that Mr Woldbye slept as the major disruption unfolded on 21 March.
However, when asked by the Daily Mail, a Heathrow spokesperson described the Sunday Times' account of events as "ill-informed misinformation".
"Thomas, and his whole senior leadership team, were exactly where they were supposed to be during an incident of this scale," the spokesperson had said.
