The line could open for service by as soon as 2033, the authority projects. Stations are slated for San Francisco International Airport/Millbrae and the Caltrain Mission Bay station at Fourth and King streets, which would eventually be replaced by a station in the basement of Salesforce Transit Center.

Major hurdles to the project remain. For starters, California hasn’t figured out where it will get up to $25 billion needed to build the San Francisco and Silicon Valley bullet-train extensions.

Nevertheless, approval of the project’s final spur north into the heart of the Bay Area is a significant milestone. It’s also the latest in a series of wins for high-speed rail in recent months, a reprieve after years of spiraling costs and litigation caused some Democratic state legislators to consider pulling the plug.

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