Can air travel industry really go green?

Boeing, Airbus, and dozens of airlines that fly their jets are jumping on the environmental bandwagon, touting "green" technology at the Paris Air Show and pledging to spew less noxious fumes into the planet's skies.

So far, though, growth in worldwide air travel is outpacing industry progress in reducing aircraft emissions. And it was chiefly high fuel costs and fear of government-regulated emissions cuts _ not concerns about global warming _ that inspired the sector's efforts to pollute less.

Air travel is growing at about 7 percent each year, according to industry trade groups. Meanwhile, technological developments are boosting airplanes' fuel efficiency by about 1 to 2 percent a year. Also, since airlines keep aircraft for decades, tomorrow's "clean planes" will be flying alongside fuel-guzzling craft of a generation ago.

Environmental groups say the only solution is to fly less _ an alternative no one at the air show was eager to discuss.

"Not flying is simply not an option," said Airbus chief operating officer, Fabrice Bregier.

Instead, manufacturers are racing to make engines that burn less fuel more slowly, experimenting with ways to dilute fuel and reduce leakage, and trimming weight of hulking jets by using lighter composites instead of standard steel.

Nearly every major exhibit at this year's show at Le Bourget, from Rolls Royce engine designers to Russian fighter jet maker Sukhoi, included references to protecting the environment. One strategically located stand, of France's CGM Group, had its walls and floor coated in artificial grass.

The race to make the world's cleanest jets resembles the trans-Atlantic battle over plane orders, as Boeing Co. and Airbus jockey to stay in the forefront. Experts disagree on who's winning, since emissions calculations depend on how full the aircraft is and how airlines configure their planes, among other variables.

Boeing recently created an office of environment management, and the Chicago-based company says its 787 Dreamliner is an environmental standard-bearer _ and that its fuel efficiency is part of the reason it's selling so fast. In a recent market report, Boeing predicts growth in nonstop regional routes, which burn less fuel than trips with a stopover since takeoffs and landings use more fuel than cruising.

Airbus says its A380 superjumbo is the cleaner plane per mile (kilometer) traveled and per passenger.

The aviation sector is responsible for about 4 percent of the world's carbon dioxide emissions, according to European Commission studies, though other estimates vary from 2 to 9 percent. The world's automobiles collectively emit much more.

Joao Vieria, aviation analyst at Brussels-based watchdog Transport and Environment, said: "The growth in aviation will change the relationship, and offset any reductions by new technologies." He predicted that airline emissions would double in the coming 20 years even as other industries' emissions shrink.

Planemakers say they are being unfairly painted as "dirty."

"I think the airline industry is, unfortunately, one of the most visible and picked-on targets in terms of noise and pollution," said Steve Udvar-Hazy, chief executive of Los Angeles-based International Lease Finance Corp., the world's largest airline leasing company.

"The noose is going to tighten around the neck of the industry and drive us to more fuel efficiences and we need to tap the best technology out there," he said.

European Union regulators say technology alone is not enough to limit emissions, and wants to include airlines in its carbon trading system. U.S. regulators bristle at the idea.

European and American officials agreed this week, however, to work together to improve air traffic control to avoid the waste that comes from circling or sharp or circuitous descents. Today's air traffic control structure dates from 40 years ago, when the jet plane came into widespread use.

Already, Delta Airlines has experimented with new arrival approaches at its Atlanta hub, as has SAS Airlines in Stockholm.

At SAS, the tests included calculating flight plans in advance and landing planes more gradually than usual. Based on those tests, SAS projected that it could save 23,000 tons of carbon dioxide annually and millions of euros (dollars) if it were to apply it to all its flights in and out of Stockholm.

On Wednesday, EU officials launched an ambitious plan aimed at slashing aviation emissions and noise by about half by 2015, based on euro1.6 billion (US$2.14 billion) in research funded by the EU and the aeronautics industry. The research is to focus on new wing design, cleaner engines, innovative rotor blades, more efficient flight paths and ways to use more renewable and recycled materials.

Environmental groups have tapped public concern about air travel's contribution to global warming. Alternative jet fuels have gained greater credibility in recent years, but still played only a minor role in this week's air show.

Farther on the horizon are proposals for a totally different plane shape, including a "flying wing" that looks nothing like the standard jet form in use for the past 50 years, said Christiane Michaut of France's ONERA state research institute.

Joss Garman of activist group Plane Stupid isn't holding his breath.

"There won't be any significant breakthrough for at least three decades. There is no technical fix," he said. "All we can do is reduce the amount we fly."

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Associated Press writers Laurent Lemel and Jane Wardell in Le Bourget and Aoife White in Brussels contributed to this report.