SFO has an occasional tour. It costs frequent flyer miles. It's oriented towards FFs who basically live at the airport anyways and wanted to see what is beneath

SFO has an occasional tour. It costs frequent flyer miles. It's oriented towards FFs who basically live at the airport anyways and wanted to see what is beneath them. They exist (MileagePlus) but are usually announced on email lists to the FFs themselves. https://www.flyertalk.com/forum/united-airlines-mileageplus/1979195-august-22-23-sfo-maintenance-tour.html https://www.flyertalk.com/forum/united-airlines-mileageplus/...