Aircraft aren't subject to the same strict fuel-efficiency standards as cars, but they're still responsible for large amounts of carbon emissions.
According to one recent estimate, commercial aviation is responsible for about 2 percent of the carbon dioxide emitted by human activities--or just slightly less than the total emissions of Germany.
And while it's known more for its space activities, NASA is working to address the issues around carbon emissions by airplanes.
Among other projects to improve the efficiency of aircraft, NASA is experimenting with a hybrid airplane engine at its Glenn Research Center in Ohio.
The aircraft hybrid system would use electric motors working in concert with a jet turbine, like the ones used in today's commercial airliners, according to Popular Science.
Fossil-fuel and electric power sources will work together to "distribute power throughout the aircraft in order to reduce drag for a given amount of fuel burned," Amy Jankovsky--a NASA engineer--told the magazine.
Southwest Airlines Boeing 737 (Image: Flickr user Aero Icarus, used under CC license)
Researchers believe a commercialized hybrid propulsion system could reduce fuel consumption by up to 30 percent compared to traditional aircraft.
Considering that commercial in the U.S. guzzled over 8.9 billion gallons of fuel last year, that adds up to significant savings.
Right now, researchers are focused on lightening and fine-tuning the system's electrical components, including the motors and even seemingly-minor details like the insulation around the wiring.
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While engineers at the Glenn Research Center continue work on the hybrid-engine project, other NASA researchers are experimenting with ways to reduce aircraft emissions.
At the agency's Armstrong Flight Research Center in California, a project called LeapTech is taking shape.
It involves testing many small electric motors as a possible replacement for large jet engines, as part of a concept called "distributed propulsion."
NASA LeapTech electric-motor research project (Photo by Joby Aviation via NASA)
Commercial applications could include an array of electric motors with a jet-engine generator, or electric motors teamed with one or two smaller jet engines for propulsion.
Right now though, engineers are merely testing motors on a wing mockup mounted to the back of a truck. They hope to begin trials with an actual airplane soon.
All of this may prove interesting to commercial airlines, as fuel makes up a large chunk of their operating costs.
And if the U.S. Envrionmental Protection Agency follows through with proposed plans to regulate aircraft emissions, improvements may become mandatory as well.
[hat tip: Randall Hamlet]