The number of aircraft being forced to circle while waiting for a landing slot will be cut after a trial of technology at Heathrow reduced stacking times by a quarter.

The national air traffic control service, Nats, said that the average amount of time each Heathrow-bound aircraft spent in holding circles had been cut from 8½ minutes in 2014 to 7½ minutes this year, the equivalent to 3,000 hours.

In August, when air traffic is busiest, stacking times were cut to 6½ minutes.

Nats said the fall had saved more than 35,000 tonnes of CO2 being released into the atmosphere over the south-east over three years.

It revealed that the reduction had been achieved after the introduction of speed limits when delays start to build up, The Times reported.

Controllers co-ordinate with counterparts in Ireland, France and the Netherlands to slow aircraft down over the Atlantic, Channel or Continent.

Nats also introduced technology to cut delays caused by winds at Heathrow.

The system, employed last summer, uses radar to bunch aircraft closer together on approach, cutting wind delays by more than half.