A consultation document - produced in anticipation of the review last November - did not mention the proposal. But following lobbying by local authorities and Labour MPs, ministers have decided to look at the radical plan.
The move is likely to anger airlines, who say the night flights are essential to "overcome daytime congestion". Heathrow is filling up: the airport currently handles 425,000 flights a year.
British Airways has argued it should be allowed to increase the number of night flights because it is running out of space within the present limits.
The new Terminal Five, proposed by BAA, the company that owns Heathrow, would alleviate congestion. BAA has told the public inquiry into Terminal 5 that noise levels would not need to increase if the terminal went ahead. This is disputed by campaigners against the terminal.
Many observers say BAA would give up night flights if this were a condition for getting the fifth terminal built. A company spokesman denies this: "It's an idea that has been floated - but not by us. We have committed ourselves to keeping to the present levels."
Campaigners against night flights welcomed the Government's move. "This is something that affects thousands of people who live in west London and the Home Counties," said Tony Colman, Labour MP for Putney, who has led the campaign to ban night flights. "What BAA and the airlines have to realise is just how bad the problem is for people near Heathrow."
Government figures show that on Christmas morning two years ago, there were 40 flights arriving between midnight and 7am. The most bitterly resented flights are the 16 that arrive daily from 4am to 6am. Night flights cannot be louder than 89 decibels - but this is still louder than a passing lorry.
Eve and Lucy Edmunds, aged four and five respectively, from East Twickenham, are regularly woken early in the morning by passing jets. Their father, Nick, says it has affected their concentration during the day and they often run to their parents' bedroom in fear.
"Young children need their sleep," said Mr Edmunds, a technology writer. "Being woken in the middle of the night by aircraft is the most terrible thing for children. It means their schooling is affected because they tend to be more tired than normal and consequently not as well behaved."
Mr Edmunds claimed things had got worse. "When we first moved in, planes started coming in around 5am. Now they start at 4 o'clock," he said. As the hours that define the "night flying time" have been altered, so the number of flights in the early hours has doubled in a decade.
Local authorities have also registered their complaints. Edward Lister, the Conservative leader of Wandsworth council, has called on the Government to set up an independent regulator to control aircraft noise. "There is no justification for night flights in an urban area," he said.
Additional reporting by Nicholas von HerbersteinReuse content