No upgrade @ 5 AM for a 7 AM departure. Decided to check in on line for boarding passes before going to the airport. Was upgraded at the airport for both my son and me (same PNR). Adjacent seats to MSP, 1d/4d seats from MSP to TUS. I am not sure what the learning is here, other than NOT checking in on line did not result in an upgrade via "the sweep" and I did not suffer by not checking in on line and was still able to get the upgrade at the airport. Complicating variables: companion upgrade on same PNR, direct flight with a stop and equipment change, platinum status, B fare ($$$).