As Heathrow starts to get back to normal, the UK Government has ordered a probe into the power outage which caused mass disruption.
The outage was caused by a single fire at an electricity substation.
Travellers are still being warned to expect delays and cancellations today - but the airport has re-opened.
UK correspondent Enda Brady says over 1300 flights were cancelled - creating global travel chaos.
"It's a national embarrassment. The Government has moved very, very quickly to call an urgent investigation, so we'll wait and see what comes out of that."
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