Sustainability and Environment
Alternative fuels still face hurdles
The alternative aviation fuel industry continues to conduct flight tests to validate the use of new jet-fuel blends.

The alternative aviation fuel industry continues to conduct flight tests to validate the use of new jet-fuel blends. At the end of April, United Airlines became the first U.S. commercial carrier to fly using a certified synthetic-fuel blend that received ASTM approval last year. The 40/60 mix powered one of the engines on an Airbus A319 in an engineering validation flight that departed Denver International Airport and reached an altitude of 39,000 feet. The drop-in fuel, supplied by Los Angeles-based producer Rentech, was derived from natural gas and converted to liquid through the Fischer-Tropsch process.