Plus, what you can do to reduce your carbon footprint.

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Airports use electricity and chemicals; passengers toss water bottles and food wrappers. But the biggest problem with air travel is air pollution: aviation accounts for about 2 percent of global CO2 emissions, according to the Air Transport Action Group, an industry organization. “Every time you take a long-haul trip, you are likely to double your annual carbon footprint,” says Harvard’s Epler Wood. Spurred on by the bottom line, popular interest, and the UN’s COP21 climate talks last year, the industry is trying to improve. But that’s not enough, Epler Wood says; travelers need to cut back to make up for the growth in their numbers. Here’s how.

What Airlines Are Doing

Replacing planes.

Boeing’s new 787 Dreamliner is designed to use about 20 percent less fuel than a 767, and Airbus claims the A320neo is 15 percent more fuel-efficient than comparable planes.

Adding winglets.

The small, upright wing extensions reduce drag, save fuel, and cut emissions. Alaska Airlines says retrofitting winglets onto its 737s saved 600,000 gallons of fuel in 2014 alone.

Lightening up.

Less weight means less fuel burned. By replacing paper flight manuals with iPads, American Airlines saved more than 400,000 gallons of fuel a year.

Using biofuel.

Carriers including Finnair, Air France/KLM, and Virgin Atlantic are turning to alternative fuels, whose production (growing plants) absorbs carbon. A caveat: the Natural Resources Defense Council points out that biofuel, if not produced sustainably, can be more polluting than petroleum.

Plane Environmental Impacts
Credit: Luci Gutiérrez

What You Can Do

Combine vacations.

Instead of taking several weekend jaunts—each requiring flights—take one longer vacation with a single round-trip.

Fly economy.

A World Bank study showed that the carbon footprint is four times higher for a business-class seat than for economy because of the weight of larger seats, extra crew, and niceties such as real plates.

Take nonstop flights.

Planes use more fuel during takeoff and landing than while cruising. You’ll also be traveling a shorter distance.

Stay close to home.

Shorter flights equal reduced emissions—or, consider taking a train.

Buy carbon offsets.

Most major airlines make it easy to balance some of your impact by supporting third-party environmental projects; United and Delta even let you use frequent-flier miles to pay.