Want to fly with a green conscience? Fly United Airlines, airberlin, Qantas or Air Canada.

Because according to the 2013 Eco-Aviation Awards hosted by Air Transport World, these are the greenest airlines in the world, whether it be for building a fuel-efficient fleet, making concerted efforts to reduce fuel burn or exploring sustainable fuels.

At the top of the heap is US carrier United Airlines, which took the top prize as the Gold Eco-Airline of the Year for its “realistic and practical approach to environmental action,” said magazine editors.

Last year, the airline saved 83 million gallons of fuel by replacing its fleet with more fuel-efficient aircraft, thereby reducing its carbon emissions by 811,000 metric tons.

It’s also on track to meets its 2013 goal of reducing fuel usage by 85 million gallons and associated carbon emissions by nearly 828,800 metric tons.

Editors likewise lauded the carrier for spearheading talks on sustainable biofuel initiatives: United undertook the first US commercial flight powered by advanced biofuel in 2011.

And since 2008, the airline has recycled more than 23.5 million pounds of aluminum cans, paper and plastic items from flights and other facilities.

Airberlin, meanwhile, took the silver award for being the first European network carrier to decrease fuel burn per 100 revenue passenger kilometer (RPK) to 3.4 liters, resulting in the reduction of total CO2 emissions by more than 100,000 tons.

Australian carrier Qantas took home the Eco-Pioneer of the Year award, for being an industry leader in exploring sustainable fuels long before the term “eco-aviation” became known, editors said.

And a partnership between Air Canada and Airbus was also recognized for an initiative made last year in which strategies like best practices, optimized operations, air traffic management, and alternative fuels helped slash CO2 emissions by more than 40 percent on a flight between Toronto and Mexico.

Meanwhile, want to feel less guilty about your flight? Several airlines such as Qantas, United, easyJet and Cathay Pacific, as well as airports in Manchester, Stockholm and SF offer carbon offset programs that allow you to make a donation towards an environmental program to render your trip “carbon neutral.”