Usually 2 hours before the first flight out
Yes. I took a flight out at 6:30 the morning and arrived at the airport @ 5AM and there are so many people there. I am almost 100% sure the airport opens 24hrs but the earliest flight out is around 6 something. Fyi, I think TSA opens at 4:30 for early departure. It is very much SJC opens 24hrs but there is a FAA regulation to prevent airplane taking off after midnight because the airport noise issues.
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