Originally Posted by
Often1
DL uses sophisticated anti-fraud software. Anyone who tells you to skip the SM # or drop a middle name or somesuch is basing their advice of 10-year old software.
DL may well cancel one or both tickets. Where are you then?
Doing this is all up to you and your risk tolerance.
I did say there was still a risk.
But I've booked myself, using SM# on both bookings, on multiple conflicting flights many times and never had a problem. DL phone agents have even advised me of no need to cancel the conflict since doing so would trigger an unnecessary add/collect. All this despite some FTers advising that the world would end if I did this.
Granted, the only times I have booked myself twice on the exact same flight was in a situation like OP, where a lower fare came up but I didn't want to release my existing booking until the new fare had been secured - and in those cases my double bookings only existed for a few minutes, not days.
Yes, it's all up to OP's risk tolerance. He/she could also call DL and just tell them what he is trying to do, and they could perhaps note a PNR that it will be cancelled by 1/1. Or they can go ahead and book into the new fare but hold reticketing until the change fee add/collect is processed (which OP would call back in to deal with on 1/1).
If someone wanted to pay in person for a change fee, isn't there a way that they can call in for the change, and then have several days after that to go by a ticket counter to pay the fee and finish reticketing?