The boss of Heathrow came under fire for an 18-hour shutdown at the airport last month after an airline representative said he had raised concerns about the hub's resilience days earlier, as lawmakers scrutinised the nationally embarrassing incident.

“Clearly Heathrow is a very significant hub operation – it has over 80 airlines operating through the airport, it is the hub for the UK and it’s the major hub for Europe, we contest – and as such we need to make sure it is resilient.

Inconvenienced passengers, angry airlines and concerned politicians all want answers about how one seemingly accidental fire could shut down Europe’s busiest air hub.

UK MPs have been grilling company representatives involved in the response to a Heathrow Airport power outage that saw flight operations grind to a standstill.

Heathrow Airport was warned about the "resilience" of its power supply in the days before a fire which shut down the airport for more than a day last month.

The official said he had raised concerns about Heathrow’s electricity supply days before a power outage forced it to shut down. Heathrow disputed the relevance of the official’s comments.