I was doing SEA-IAH-NRT run on CO back in May. Since I was based out of DTW, I had to booked a separate DTW-SEA on NW on a cheapo K fare. It was the last flight of the day and it got mechanical. By the time I got to SEA, gate was closing and I lost my confirmed F seat. Gate agent told me I could still board but I would be sitting in coach. Since there was another flight a little over an hour later so I got on that one and got the gate agent confirm me in F. So at the end of the day, I still made my run, and almost 30K EQM richer.