I'm a lowly 2P and was booked in Y on a UA flight last week from DSM to ORD. When I booked my ticket about 10 days before departure UAL's website showed 3 seats in F on the outbound and 5 seats in F on the return flight (same day--out in the morning back in the late afternoon).

Then, from about 4 days out until I checked in online both flights showed 0 seats in F. So, I figured my upgrade hopes were dashed. When I completed my checkin process online I was shocked to see that my upgrade request had been confirmed for both flights.

Nice surprise...but how did that happen?