Three years after the extension opened, ridership is nowhere near what BART officials had hoped. The route is losing money, and BART is embroiled in a funding fight with another Peninsula transit agency. Prior to construction, BART projected there would be 17,800 average daily boardings to and from the airport by the year 2010. During the first year of operation that began in 2003, there were 5,864 daily boardings, the second year 6,675, and the third year 7,116. Likewise, ridership to and from the three other stations on the airport extension route -- in South San Francisco, San Bruno and...