Following over 1,000 flights grounded on Friday, around 250,000 passengers travelled in and out of the airport on Saturday.
Sunday saw more or less a full schedule with some delays.
It expects little to no disruption today.
“We have welcomed the government’s announcement of an investigation into the cause and response to the off-airport power outage and have launched a review, to be chaired by former transport secretary Ruth Kelly, of Heathrow’s response,” the airport said.
“While these inquiries are ongoing, our focus remains on serving our passengers.”
Energy secretary, Ed Miliband ordered a full investigation of the substation fire which caused the power outage.
The Met police said there was no evidence the fire was an act of sabotage