United Airlines Friday said it completed the first flight by a U.S. commercial airline using natural gas synthetic jet fuel.

"This flight confirms our assumptions about how this fuel performs on a commercial aircraft and is the next step in our effort to stimulate competition in the aviation fuel supply chain, promote energy security, environmental benefits, and the creation of green jobs," Joseph Kolshak, United's senior vice president of operations, said in a news release. "United continues to support the use of alternative fuels, and we urge the U.S. government and the investment community to further support critical energy opportunities."

United used Rentech natural gas-derived certified synthetic jet fuel in a 40-60 mix with conventional Jet A fuel in one of two engines of an Airbus 319 on a flight from Denver to an altitude of 39,000 feet, with several maneuvers, including taxi, takeoff, climb, cruise, auxiliary power unit start, descent and approach. An onboard team collected data on the performance of the fuel, United said.

Rentech President and Chief Executive D. Hunt Ramsbottom said: "Today's engineering validation flight is a significant step forward for the commercial aviation industry. We are proud to collaborate with United Airlines to demonstrate the viability of certified synthetic jet fuel that delivers on performance and safety expectations required by commercial airlines, along with environmental benefits that exceed that of conventional jet fuel."