Had a great trip down to MEX last weekend. Flew DL to LAX and connected to the daily AM 787 to MEX. The flight down we were upgraded a few days out and there were no issues. On the return, we never cleared into Biz and about 24 hours out the 787-800 was subbed with a -900, sending us from row 21 to row 36. I called into the call center about our worse seats and the upgrade waitlist and was told that my Delta Platinum card needed to be verified at check-in (??). At check-in the next morning, I asked the agent about the upgrade list. He did lots of trying and said it was longer than the number of seats and I asked him to add us anyway. He was surprised when he did thet then said we were number 8 and there were 12 seats available. When we got to the gate, I asked about the upgrade and was told that if it happened it would automatically when I went through the readers -- but that did not happen. I stopped at the podium and after much typing and discussion they gave me a boarding pass for 4A but said they could not upgrade my companion because she did not appear on the upgrade waitlist. We argued for awhile but they gave me the choice of going with 1 seat in biz or none, but eventually moved one seat to 18F and we got on the plane. The business class cabin had 11 out of 36 seats open.... so there was no reason they could not have upgraded her.

Is this typical for flying Aeromexico? Was this a screw up by the check-in agent who failed to add both of us to the list? Was there really, nothing, they could have done? Or did I do something wrong? There was certainly no clearance at 120 hours as expected....