Delta PM, DFW-SLC-PDX on Thursday, then SEA-SLC-DFW yesterday (yes, I hate American this much).

Thursday SLC-PDX I was number 2 of I don't know, 10 or so with 6 seats open. Last I checked the UG list for that connection was at boarding in DFW.

Get to the gate at SLC and no upgrade at boarding, but all the seats have disappeared, number one got an upgrade but I didn't. But the other five seats are now unavailable. No biggie but strange.

Measly boarding group for prem, so when I board with sky and notice some half dozen FC seats empty, I tell the FA I was next on the list and I'm in 11E. He says no prob and thanks, he'll make sure they don't fly empty. So I settle in my C+ middle seat 'upgrade' and watch boarding.

Literally the last five people to board the aircraft take those seats, the bulkhead row 1 and a random 3B or something. The folks in the front row, well, let's just say they didn't match the average profile of DMs, a grungy oily haired biker guy and his equally grungy girlfriend, a young couple who seemed a little enamoured with their 'first class' seats on a quick hop to Portland, and guy number five looked like he ought to be there.

Obviously, I survive with no scratches and live to fly another day and forget about it about the time the door closes.

Except, SLC-DFW the next day, again, I check at boarding for SEA-SLC and now I'm 1 of 5 with six available seats on SLC-DFW. By this time I had completely forgot about the day before. I was so confident when I landed in SLC that I sauntered over from E to C for the 35 minute connection and didn't bother to grab anything to eat - I knew they'd feed me in FC.

Nope. Someone has bumped me from one to two - and that guy got an UG, but the remaining 5 seats are gone. Zero available in FC - and this happened between me taking off from SEA and landing in SLC, assuming the app is always up to date.

Now, I really and truly don't care that much, DMs deserve upgrades, and Delta is free to try to sell an FC seat before they put me in it on an economy fare to drink all their Woodford. And I appreciate upgrades, but until I can get my home office to agree to purchase FC for me, which seems unlikely, I'll continue to play roulette with upgrades, no big deal. This just happened to be statistically improbable - I.e., I haven't see seats just disappear like that, I wouldn't bother to post if this was a common occurrence. It isn't. Usually there is a trickle of last minute checkins that move the list around, but I've never seen half an FC cabin fill up in the last couple hours before boarding with folks who were not on the list.

So I'm just curious, what happened?