assenger planes are to be towed to runways with their main engines off, reducing their environmental impact, in a trial at two UK airports.
The short trials involve Virgin Atlantic passenger jets at London's Gatwick and Heathrow airports.
Gatwick hopes to be the first airport to implement the system, which it is claimed could save two tonnes of fuel per plane.
Environmentalists complain that is only 3% of fuel for a transatlantic flight.
They also say towing all aircraft would be unworkable at busy airports.
BBC Transport Correspondent Tom Symonds says aircraft engines are at their least efficient on the ground.
The trial involves towing the planes from the departure gates to a so-called starting grid next to the runway, where their engines are fired up, he said.
Virgin Atlantic claims its planes use up to 1.5 tonnes of fuel just getting to the runway. Another half a tonne could be saved at the other end of the journey.
The airline says a number of American hubs are also interested in starting their own trials.
Chancellor Gordon Brown announced air duty increases as an environmental measure as part of his 10th pre-Budget report last week.