Interesting that the skycaps at MSP, DTW, and MEM are NW employees and not employed by an airport service agency.

At ONT, all (I think) the skycaps work for Sierra Aviation and at least one of their jobs is to move bags from the back side of TSA screening back to the airline's belt. (At ONT, you checkin, then bring your own bag to TSA and wait while they screen it, then the skycap brings it back to the airline.)
Sierra also handles NW's bag problems when the ticket counter is closed. There is a sign on the window of the Baggage Service office saying that if the ticket counter is closed, and Sierra employee can get the bag out. Already dealing with irate customers some of the time.