Heathrow has been granted a surprise six month extension to the second phase of its controversial runway trials.

BAA’s first test, which lasted four months, led to a six-fold increase in the number of complaints about aircraft noise in November last year.

Its second phase - due to start on July 1 - had initially been due to last until September 30 but Aviation Minister Theresa Villiers announced this week it would continue for a total of nine months, ending in March, 2013.

Ms Villiers also granted permission for aircraft scheduled to arrive after 6am to land between 5.30am and 6am, in return for fewer flights between 4.30am and 5am.

BAA said the measures - which allow it to use one runway simultaneously for arrivals and departures when planes face a 10 minute wait to land or take off, or if 30 per cent of all aircraft are running more than 15 minutes late – would improve punctuality and reduce delays and give the airport “greater resilience” during the Olympics.

Tim Hardy, BAA’s airside director, said: “This trial does not mean an increase in the number of flights operating in and out of Heathrow.

“However, with Heathrow operating at full capacity, we need to look at ways to strengthen resilience, which will bring benefits to the local community through fewer late-running flights, to passengers by providing a more punctual service, and to the environment by reducing aircraft stacking and emissions.”

John Stewart, chairman of campaign group Hacan, said: “The big concern of local people is that they will lose their half day’s break from the noise. It is this which makes life bearable for so many people. “There will also be a lot of anger that more flights are being allowed before 6am.”

BAA said the Civil Aviation Authority’s report on the first phase, between November 2011 and February this year, noted the airport achieved improved punctuality, reduced aircraft emissions and a lower number of planes having to taxi across runways. The air operator said it could not be sure the higher number of residents complaining about noise was a direct result of the test.

The Conservative leader of Richmond Council has said he “totally disagrees” with fellow Tory peers who have called for the Government to abandon its opposition to a third runway at Heathrow.

Lord Spicer and Lord Tugendhat both warned of the consequences of refusing to expand the airport.

Lord Tugendhat, speaking at Lords question time this week, said: “If the Government refuses to allow a third runway at Heathrow it will be imposing a brake on the growth of the British economy.”

Lord True, the Conservative leader of Richmond Council, said: “I totally disagree with the view of those peers and so do the vast majority people of all parties in west London.

“There should be no Heathrow expansion – period. It was this Government that ruled out, and continues to rule out, the third runway - and I would oppose any attempt to resurrect it.”