However Heathrow's operator, BAA, said it "provided no extra runway capacity" and that the idea also faced "seemingly insurmountable technical, operational, political financial challenges, and would take many years to deliver".

The scheme, which would create a so-called "virtual hub" running from west London to West Sussex, has been welcomed by Gatwick Airport,

However Heathrow's operator, BAA, said it "provided no extra runway capacity" and that the idea also faced "seemingly insurmountable technical, operational, political financial challenges, and would take many years to deliver".

The scheme, which would create a so-called "virtual hub" running from west London to West Sussex, has been welcomed by Gatwick Airport,

Anything which provided "short to medium-term alleviation of capacity issues in the South East" should be considered, although the funding and route would need careful consideration, a spokesman said.

The issues of aviation congestion, and links between airports, have been a topic foe discussion recently.

One idea is a £40bn terminal in the Thames estuary several miles off the Essex and Kent coasts.

Currently Heathrow and Gatwick are linked only by road, or by travelling into London and back out again by rail. There has also been discussions about extending high speed rail services to Heathrow.

The DfT said ministers wanted a policy "which supports economic growth while addressing the environmental impacts of flying".