Expect longer security checkpoint lines at San Francisco Airport
As you get ready for your flight from San Francisco Airport, please note that Transportation Security Administration (TSA) security checkpoint lines may be longer than normal.
We recommend arriving at the airport earlier than usual to allow enough time to get through security. Also, to help make the security screening process as smooth as possible, please ensure that you’re familiar with our carry-on baggage policies: https://www.united.com/carryonbaggage
No mention of why. Maybe they have me on record as opting-out of the full body scanners, and a groping takes longer.