SAN FRANCISCO (CBS SF) — Widespread, dense fog delayed holiday travel plans at San Francisco International Airport during a heavy travel day, airport officials said Friday.

As of 12:30 p.m., 215 flights had been delayed and 20 were canceled, throwing hundreds of travelers off schedule.

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“We are delayed one to two hours because of fog,” said Vanessa Weiser of Dublin.

AAA said 7 million Americans are flying this holiday season, the most to pack airports since 2003.

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Officials at Oakland International Airport said more than 25,000 flights are going out Friday and that the airport is expected to stay extra busy until Jan. 5.

KPIX reached out to Mineta San Jose International Airport about its holiday travel estimates, but we have not yet heard back.

The airport advises travelers to arrive two hours prior to departure for domestic flights and three hours prior for international flights.

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Rain returning to the Bay Area this weekend could also give rise to more travel issues.