Complaints about noise from planes at Heathrow Airport have risen more than six-fold during a trial changing the way its runways are used.
The scheme, started in November, has made it easier to for planes to use the airport's two runways simultaneously.
There were 480 complaints in the first month of the trial, compared with 75 during November 2010
"BAA has worked to maintain an open dialogue with local residents on the trial," the airport operator said.
"After the first part of the trial is completed on 29 February, we will be able to share more findings and have a greater understanding of the impact of the trial on local communities," it added.
Coinciding with Olympics
When the trial began, BAA has warned that communities may lose their respite periods.
Previously the runways were restricted to take-off or landing and switch each afternoon, except in an emergency, to give residents respite from the noise.
Under the changes, dual use of the runways can be deployed when a plane faces a 10-minute wait to land or take off and if 30% of all flights are delayed by more than 15 minutes.
Before the trial, the average time delay for flights at the west London airport was 12 minutes.
BAA insisted the number of flights at Heathrow would remain capped at 480,000 aircraft movements a year.
The first trial finishes on 29 February while a second will run from 1 July 2012 until 30 September - coinciding with the London Olympics.
The trial was recommended by the Department for Transport and will be overseen by the Civil Aviation Authority.