Heathrow's chief has said he would look at scrapping night flights altogether were it a condition for expansion to be allowed.
The airport operator has already promised there would be no more flights before 6am than at present if a third runway is built.
But campaign group HACAN believes a new landing strip should make it possible to ban them altogether, ending one of the biggest bugbears for those living under the flight paths.
Heathrow CEO John Holland-Kaye this week refused to rule that option out.
He told getwestlondon the airport would look at ending night flights should that be one of the Airports Commission's requirements for a third runway to get the go-ahead.
"We need to get the right balance of doing the right thing for the community while still operating as a thriving airport," he said.
"If we have too many constraints you end up with something that just isn't effective anymore in doing the underlying job of the airport to connect businesses and goods worldwide.
"The flights we have in that early morning period are going to some important trading routes. The people sitting on those planes are often local people who need to get to London early in the day to do business.
"Let's see what the commission says on balance. Whether we could end night flights would depend on what the (commission's) other conditions are. We need something that balances all the conflicting needs."
At present, between 16 and 18 planes land at Heathrow between 4.30am and 6am each day.
Mr Holland-Kaye was speaking to getwestlondon following the launch of Heathrow's new 10-point plan to reduce emissions.
He also said the airport had no plans to review its existing compensation scheme for those affected by noise if it does not get the go-ahead for a third runway.
Heathrow announced in February it would increase compensation for those affected by aircraft noise from £30m at present to £700m with a new runway.
It also said it would adopt the more generous European noise measure to calculate which homes were eligible, as used at other major European airports, rather than the statutory UK government standards.
But Mr Holland-Kaye made it clear that offer was only on the table if it gets permission for a third landing strip.
"What we're offering [with a third runway] goes beyond government standards. We don't have any plans to go beyond those standards without a third runway," he said.
"Expansion would allow us to take some transformative action because we would have more trade to pay for things.
"If a business isn't expanding it has to continuously reduce costs. At the moment we're reducing our cost base by £600 million over the next few years."
The Airports Commission is weighing up rival bids for a third runway at Heathrow and a second at Gatwick. It is expected to publish its recommendations in late May or early June.