Officials and travelers are calling for an investigation into not only how the blaze started, but how it was able to cause such a large disruption to global travel.

Flights are now landing and taking off at Heathrow after Friday's fire at a nearby substation shut down Europe’s busiest airport for most of the day, causing major disruption

London's Heathrow Airport resumed full operations on Saturday and ordered a probe into how it dealt with a power outage that shut Europe's busiest air hub for almost a day as airlines warned of further delays and cancellations.