Paul Sakuma/ASSOCIATED PRESS
** FILE ** In this July 31, 2006 file photo, a United Airlines plane leaves San Francisco International Airport. United has invested in flight planning software that helps pilots choose the best routes and speeds. In some cases, that means planes fly at slower speeds. United estimates the software will save it $20 million a year in fuel and overflight costs, fees foreign countries charge airlines for use of their airspace. (AP Photo/Paul Sakuma, file)