But since air travel emissions were not regulated under the Kyoto Protocol, the international agreement signed in 1997 that set binding targets for reducing greenhouse-gas emissions, the skies aren't much greener than they were a few decades ago. And most national governments have been reluctant to impose new environmental restrictions on the already ailing airline industry.
Nonetheless, some airlines and airplane manufacturers are taking steps to improve their ecofootprints. Southwest and Continental have implemented fuel-efficiency improvements, waste-reduction programs, and increased recycling. They are also investing in more fuel-efficient airplanes. Also on the cutting edge of green is Virgin Atlantic, which made news in early 2008 when it became the first major carrier to test the use of biofuels on passenger jet flights. Now Air New Zealand, Continental, Japan Airlines, JetBlue, and Lufthansa are also testing biofuels.
Airplanemaker Boeing is developing a carbon-neutral jet fuel made from algae. Its newest commercial jet, the 787 Dreamliner (now in final testing before late 2010 delivery to several airlines), is 20 percent more fuel-efficient than its predecessors, thanks to more efficient engines, aerodynamic improvements, and the use of lighter composite materials. Airbus is also using more lightweight materials in its new planes.
On the far end of the innovation spectrum are zero-emission airplanes that use little or no fuel. The French company Lisa is building a prototype small plane, dubbed the Hy-Bird, that uses solar power (via photovoltaic cells on its elongated wings) and hydrogen fuel cells to fly with zero emissions – and nearly no engine noise. The company claims the Hy-Bird is the first 100 percent eco-friendly plane.
Even more unusual is the fuel-free plane dreamed up by Mississippi-based Hunt Aviation. It's working on a prototype small plane that uses helium-filled pontoons, an onboard wind turbine, and a battery to fly without using any fuel at all.
Don't look for these planes on airport runways anytime soon, however.
Until then, try to take a train or bus instead. If you must fly, consider compensating for your flight's emissions by buying a carbon offset from a firm that will use the money to fund alternative energy and other greenhouse-gas reduction projects – but first do your homework on offset programs.