Originally Posted by
railroadtycoon
I was offered an upgrade once for $500 USD from Y to C once at checkin at IAD. I was told that that Y was overbooked.
Yep, I had a similar upgrade from Y to C for 300 GBP, LHR-NRT. It was offered to everyone irrespective of the original fare paid. I guess this only happens if they are overbooked though.