Originally Posted by sjpmurph01

I have discussed this with TSA supervisors at PHL before. B is the primary TSA-Pre checkpoint. So if in doubt, that is where Pre is most likely to be available. A-East and C are only open at peak screening periods currently. (Can't speak for D/E as I'm never down there.)

There are US & AA kiosks and agents at both A-East & B/C, so regardless of who is operating your flight, if you have Pre it makes the most sense to check-in at B/C, and go through TSA at B. From there you can easily walk to A/B/C/D/E or shuttle to F.