Picture credit: Heathrow
More than 300,000 passengers were affected as flights were cancelled or diverted to nearby European airports to cope with the backlog of flights.
Whilst flight schedules resumed on Saturday (22 March) tens of thousands of passengers were reportedly still left stranded across the globe awaiting flights to get back to the UK.
National Grid said at 2pm yesterday the network was restored to all those customers impacted, including Heathrow airport.
But concerns have since been raised over the airport's sole reliance on the North Hyde substation for power and how back-up systems failed to keep the airport up and running in the interim period.
Willie Walsh, Director General of IATA, said: "This is yet another case of Heathrow letting down both travellers and airlines. And that begs some serious questions. Firstly, how is it that critical infrastructure — of national and global importance — is totally dependent on a single power source without an alternative.
"If that is the case — as it seems — then it is a clear planning failure by the airport. And, from that arises the question of who bears the costs of taking care of disrupted travellers. We must find a fairer allocation of passenger care costs than airlines alone picking up the tab when infrastructure fails. Until that happens, Heathrow has very little incentive to improve."
Dr. Komal Raj Aryal Lecturer in Crisis and Disaster Management at Aston University said: "The incident highlights how a localised disruption to one of the UK’s critical infrastructures can trigger cascading impacts across the globe."
Meanwhile Heathrow's Chief Executive Thomas Woldbye told BBC Radio 4's Today programme how "proud" he was of staff in their handling of the unprecedented event which he said happened outside the airport, leaving them "to deal with the consequences".
