Giant tanker aircraft would fill the tanks of up to four airliners in a single trip, reducing the total fuel burnt by about a fifth even after taking into account the fuel used by the tankers.

Aircrafts on long-haul trips, such as from London to Sydney, would no longer have to land to refuel. It would be possible to fly non-stop halfway around the world with three or four air-to-air refuellings. The risk of jets colliding would be virtually eliminated by a satellite positioning system that would allow the pilot of the tanker to control both aircraft during the refuelling. Existing technology is already extremely safe and is used to refuel Airforce One, the US President ’s Boeing 747.

The proposal has been put forward in a report by the Royal Aeronautical Society’s Greener by Design group. The group includes representatives from the Department for Transport, Airbus, Rolls-Royce and Cranfield University.

The report concludes: “The potential benefits of air-to-air refuelling for long-haul flights are sufficient to justify a rigorous assessment of it from an environmental, logistical and economic standpoint.”

John Green, the group’s senior scientific adviser, said that existing long-range aircraft were an inefficient shape because they needed large fuel tanks and big engines to propel the extra weight.

He said that fuel was so heavy that a third of what was used on long flights was burnt simply in carrying enough fuel to remain airborne for up to 18 hours. Airliners also waste several tonnes of fuel on take-off because of the enormous thrust needed to lift so much weight. Fuel accounts for almost half of the 395 tonnes that a British Airways 747 weighs when taking off from Heathrow bound for Singapore.

Mr Green said that aircraft could in future take off from Heathrow with only a few tonnes of fuel and then rendezvous over the Irish Sea with a tanker.

In terms of fuel efficiency, the optimum distance between refuellings would be 3,000 miles. Mr Green acknowledged that air-to-air refuelling would require major investment in a new fleet of tanker aircraft. But he said that little extra ground infrastructure would be needed because the tankers could use existing military airbases.

Long-range aircraft would be phased out and replaced by highly efficient medium-range jets designed to carry only enough fuel for 3,000 miles.

The Greener by Design group has previously proposed that aircraft should save fuel by stopping more frequently to fill up on long journeys. However, this idea was dismissed by airlines because trips would take longer, increasing the need to have relief crew and deterring some passengers.

Increasing the number of “hops” on a long trip would also increase the risk of a crash because take-off and landing are the most dangerous phases of a flight. Mr Green dismissed concerns that air-to-air refuelling would pose an extra risk to passengers. “If it’s good enough for the US President then it ought to be good enough for us,” he said.

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