The CEO of London Heathrow Airport was asleep and colleagues struggled to reach him during the first hours of the shutdown in March.
Some 200,000 passengers faced disruption when Europe’s busiest airport suffered a power outage due to a fire at a nearby electrical substation.
A review into the incident was published on Wednesday, shedding more light on how executives handled the crisis.
The alarm was raised shortly after midnight on March 21, as several key systems lost power and others were left using back-up energy.
However, Thomas Woldbye, the airport’s CEO, could not be reached.
The chief operating officer, Javier Echave, also attempted to call him “several times” during the early hours of the day, according to the review.
Woldbye ultimately missed the decision to suspend airport operations, which was instead made by Echave.
The CEO said he became aware of the incident at around 6:45 a.m., some five and a half hours after the airport had decided to shut down, and more than six hours after the first indication of problems.
He reported to the review that he didn’t hear the first alarm or Echave’s calls because he wasn’t aware that his phone had gone into silent mode while he was asleep.
While the CEO’s absence may have added to the stress on the day, both Echave and Woldbye said the decision to stop operations wouldn’t have changed if the latter had been involved.
The review recommended “enhancements” to the notification process of critical incidents, such as a second means of contacting key individuals.
It added that Heathrow has “taken steps” to implement this.
In total, 27 recommendations were made by the review, led by Ruth Kelly, an independent Heathrow board member and former UK transportation secretary.
“Whilst the disruption was significant, alternative choices on the day would not have materially changed the outcome,” she said in a press release.
“The airport had contingency plans in place, and the report highlights that further planned investment in energy resilience will be key to reducing the impact of any similar events in the future,” Kelly added.
A full report from the National Energy System Operator is expected by the end of June.
