Boeing will modify United Airlines’ 777 fleet with a performance enhancement performance package designed to result in greater fuel efficiency and reduced emissions, the manufacturer and United Continental Holdings announced today. Boeing estimates the package, which involves a software modification that allows for a drooped aileron, a ram air system improvement and the installation of more efficient wing vortex generators, will cut fuel spending by some $200,000 on each of 52 United 777s (assuming $100 per-barrel crude oil prices).

“We appreciate Boeing’s continued efforts to make existing aircraft more fuel efficient,” said United fleet vice president Ron Baur. “We are very focused on improving fuel efficiency in our fleet as a natural hedge against rising fuel prices.”

Continental Airlines, which merged with United last year, became among the first airlines to buy the package, agreeing to outfit twenty 777s in 2007.

Eighteen airlines with fleets totaling more than 350 airplanes have ordered the 777 performance improvement package. Designed to improve the aerodynamic performance of the 777-200, -200ER and -300 models, the program’s target audience operates more than 500 airplanes. Boeing now incorporates the upgrades in its new 777s–the 777-200LR, -300ER and 777 Freighter–during factory production.