Airport bosses hope the move will help them to reduce the delays and cancellations caused by the weather, with 700 flights axed yesterday and only a third of services taking off during the day.
Despite the runway opening and snow being cleared from aircraft docking bays, thousands of passengers were expected to spend another night camping out at the airport last night.
BAA’s chief executive Colin Matthews apologised for the disruption but warned it could be some time before normal operations resume.
He said BAA was arranging more hotel rooms, setting up marquees for stranded passengers, asking its office staff to turn up for duty to help travellers and bringing in extra contractors to clear snow.
Prime Minister David Cameron said the disruption was understandable given the severe weather, but said he was frustrated that it was taking so long for the situation to improve.
It is understood that a shortage of space at Heathrow to store the quantity of de-icer needed to tackle the problems had emerged as a key cause of the travel chaos that has hit thousands of passengers at the UK’s biggest airport days before Christmas.
Elsewhere, international train operator Eurostar said it hoped to run a near normal service today.