NASA is developing an electric airplane program that they hope to launch in 20 years. Eventually, the entire commercial flight industry will be petroleum free, if NASA has its way.

One round trip flight from San Fransisco to New York produces two to three tons of carbon dioxide per passenger, according to The Economist. To put that into perspective, an American who doesn't fly at all produces approximately 19 tons of carbon annually. Additionally, jet engines expel toxic compounds into the air which contribute to the deaths of an estimated 10,000 people every year due to asthma, lung and hear disease and cancer.

While it may be a few decades until electric engines power commercial jets, NASA has some ambitious short-term goals as well. They're working to improve engine design to reduce hazardous NOx emissions, and are also working on a hybrid gas-electric motor which could be available on small commercial flights by the early 2020s.