In what year did BART first extend to the San Francisco International Airport?

The correct answer is 2003 because that was the year when BART extended its service to the San Francisco International Airport (SFO). This extension was significant as it provided a direct transit link to one of the region’s major transportation hubs, facilitating easier access for travelers and reducing traffic congestion in the area. The completion of this extension marked a notable enhancement in public transportation options for both residents and visitors, making air travel more accessible via the BART system.

The other years listed do not correspond to this important milestone in BART's service history. Therefore, 2003 stands out as the pivotal year when the direct airport connection was established.