A BART extension to San Francisco International Airport was first proposed in 1970 - before the initial system even opened. The BART extension was constructed in concert with the International Terminal (which expanded the airport's capacity) and the AirTrain system (which connects the BART station to the other airport terminals). The San Francisco Airport Commission built the station for BART at a cost of $200 million, with BART paying $2.5 million in rent each year to use the station. The AirTrain system opened on February 24, 2003, with BART service to SFIA station beginning on June 22, 2003. The station was initially served by the
Blue Line, plus the
Purple Line, a shuttle service to
Caltrain connections at
Millbrae station. The shuttle service was discontinued on February 9, 2004. The
Yellow Line began serving SFIA station (as well as Millbrae on nights and weekends), with northbound trips on the
Red Line also serving SFIA station at peak hours. Peak-hour Richmond line service began serving the station in both directions on September 13, 2004. BART service to stations in San Mateo County is funded by
SamTrans, rather than county tax revenues. As ridership stayed below expectations, SamTrans had to pay a larger-than-planned operating subsidy to BART. On September 12, 2005, in order to lower these subsidies, BART reduced service so that only the Blue Line served SFIA and Millbrae stations. SamTrans and BART reached an agreement in February 2007 in which SamTrans would transfer control and financial responsibility of the SFO/Millbrae extension to BART, in return for BART receiving additional fixed funding from SamTrans and other sources. On January 1, 2008, BART increased service to the San Mateo stations. SFIA became the terminus of the Yellow Line at all times, and direct service between SFIA and Millbrae was discontinued. On September 14, 2009, the line was extended to Millbrae on nights and weekends, restoring direct service at those times. During its first decade of service, ridership remained well below initial projections. Ridership has continued to increase, reaching a peak of 6,788 weekday exits in fiscal year 2016. On February 10, 2020, the Purple Line began running during all BART operating hours, with the Yellow Line terminating only at SFIA. In October 2019, the BART board approved development of technology for a proposed pilot program, under which BART and other public transit riders would have access to priority security screening lines at the airport. SFO–Millbrae service ended on August 2, 2021; it was replaced by an extension of the Red Line to SFIA weekdays and Saturdays, and an extension of the Yellow Line to Millbrae evenings and Sundays. Richmond service began operating on Sundays effective February 14, 2022, providing 4 trains per hour at SFIA until 9 pm every day. In April 2022, the middle track was reopened, allowing the north platform to be used for all trains. The middle track is used for trains to Millbrae, while the north track is used for trains to San Bruno and points north. Installation of second-generation fare gates at the station took place from October 11–26, 2024. On January 13, 2025, a shuttle train began operating between SFO and Millbrae between 9 pm and midnight due to the installation of
Communications Based Train Control equipment near Millbrae. It is signed as part of the Yellow Line with timed cross-platform transfer offered at the station. ==References==