On Monday, United Airlines flew from Houston to Chicago with jet fuel made from algae. It's the first bio-fuel powered commercial flight in the United States.
Analysts say bio-fuel could eventually lead to better fuel price control for the airlines.
On November 9th, Alaska Airlines is expected to launch the first of flights powered by a bio-fuel blend made from used cooking oil.
Virgin Atlantic was actually the first airline to put a bio-fueled plane in the air, with a test flight in 2008. But Virgin has not yet flown a bio-fueled plane with passengers.