both boeing and Airbus promise that their newest jetliners will offer unparalleled fuel efficiency. that is important because a second basic theat to the future of the airline industry is the price and availability of fuel. in 2006, fuel accounted for about 30 percent of the operating costs of US airlines, up sharply from a few years earlier.for air transportation,finding a substitute for oil-based fuel is much more difficult than in group transportation because the economic viability of flight depends on the use of a concentrated from of explosive energy.there is no easy substantially for fossil fuel in this regard. still, the fuel efficiency of air transport has substantially improved in recent decades, as hight as 70 percent between 1960 and 2000, and possible future reductions are expected to take place at a rate of 1 to 2 percent per year.