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Green Aircraft and Airlines

In recent decades, airlines and aircraft manufacturers have become increasingly committed to becoming more "green," or environmentally friendly. Companies and people realize that the planet's oil resources are becoming depleted. At the same time, when you burn oil, it creates so-called greenhouse gases – particularly carbon dioxide – which have the long-term effect of increasing the Earth's temperature.

In 2007, the International Air Transport Association (IATA) set a goal of creating a "zero-emissions" airplane within 50 years, meaning the airplane would produce no greenhouse gases. And the European Union has proposed taxing airlines for their carbon emissions while the plane is in EU airspace. So what are the airlines doing today?

Ranking the Greenest Airlines

A 2013 report from the International Council on Clean Transportation ranked the fuel efficiency of the 15 largest U.S. airlines. Fuel efficient airlines burn relatively less fuel than their competitors and consequently produce fewer carbon dioxide emissions.

Alaska Airlines took top honors as the most fuel-efficient airline in the United States, followed by Spirit Airlines and Hawaiian Airlines (tied), Continental Airlines (which has since merged with United Airlines) and Southwest Airlines. Allegiant Air was the least-efficient of the 15 airlines which were evaluated, followed by American Airlines, AirTran Airways (which has merged with Southwest), US Airways (which has merged with American) and Delta Air Lines.

In 2011, the organization Bright Planet ranked the carbon efficiency of the world's most popular airlines. The study took into account fuel economy, flight distances, number of passengers per plane, seating density and freight share. Bright Planet ranked Europe's Ryanair as the most carbon-efficient airline, followed by Cathay Pacific, EasyJet, Continental and United Airlines.

The least efficient airline, according to Bright Planet, was American Eagle, followed by SkyWest Airlines, ExpressJet Airways, Southwest and Lufthansa.

Which Airplanes Are the Most Energy Efficient?

Determining a car's fuel efficiency is relatively straightforward and transparent. The average MPG for city and highway driving is advertised right alongside the sticker price. However, with aircraft, it is a bit more complicated. Fuel consumption varies based on aircraft speed, weight load and wind speed, among other factors. Although this is by no means the ultimate list of the "greenest" aircraft, we've highlighted a few eco-friendly aircraft below.

Airbus A319: The A319 is 15 percent more efficient than the similarly sized Boeing 737-300, which is one of the most inefficient commercial aircraft.

Boeing 787 Dreamliner: The Boeing 787 aircraft is designed to be 20 percent more fuel efficient than the Boeing 767.

Bombardier CSeries: Launching in the second half of 2015, Bombardier says this single-aisle jet will use 20 percent less fuel than comparable competitors' planes, including the Boeing 737 and Airbus A320.

Turboprop planes: Consuming much less fuel than standard jets, large prop planes might just be the future of short-distance air travel for cash-strapped airlines looking to cut fuel costs. However, many airlines are hesitant because the turboprops are not as fast as jet engines.

Other aircraft that are particularly fuel efficient, when measured by fuel consumption per seat per 100 kilometers flown, include the Boeing 737-900ER, Airbus A330-200 and Boeing 767-400ER.

Which Airplanes Are the Least Energy Efficient?

Airbus A380: Although Airbus had claimed the A380 would be the most environmentally friendly aircraft in the skies, fuel consumption was estimated for full flights on aircraft configured with many more seats than are actually in A380s today.

MD-82s: Because MD-82s can last more than 30 years, most of those in the skies today are relatively old and inefficient. An MD-82 manufactured in the 1980s emits approximately 21 percent more CO2 than an Airbus A319 produced today.

Other aircraft that are particularly fuel inefficient, when measured by fuel consumption per seat per 100 kilometers flown, include the Airbus A340-300, Bombardier Dash 8 Q400 and Bombardier CRJ1000.

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