Hey so I've never had any relevant status with United, but I have flown them very few times in the last years, here and there maybe once a year or so always in eco. I tend to fly and have status on OW btw, but in rare cases I have to fly United. The good thing is their miles don't expire so I had very few accumulated over the years.

Anyway, some time ago I had enough miles for a cheap economy ticket Houston-Mexico City ...I know, very short flight, nothing major. So I had an economy award ticket and during boarding when I scanned my ticket it beeped and I was assigned a new one, which had been upgraded to "first"
I definitely didn't mind but was very surprised...
The flight in eco didn't seem full so don't think it was because of that, and even if it were I would think they'd upgrade their people with status first?? And I didn't mind, there were only few of us in F, I remember the seat next to mine was empty.

Any idea why this happened? Did leave a nice impression though...I mean in the US I usually fly AA and this would never happened there lol