The FlySFO Instagram account posted that starting tomorrow (Wednesday, March 12, 2025) both the bridge and the tunnel from the AirTrain station to/from Terminal 3 will be closed. The alternate they suggest is for Premier flyers to use the E tunnel and Economy flyers to use the F/G tunnel. I will probably just use the Terminal 2 station and the bridge to the D gates. The Terminal 3 mezzanine level will be completely closed, as well.

Also - the area that was being readied in Terminal 2 for baggage drop (that I thought United could/should begin to use) is now the location for Southwest!

JK-SFO