Are you booked in Row 22 at least?
Better yet....pay for the seat so you don't have to worry about it? or use miles for the upgrade?
A transcon is no place to be hoping for a battlefield upgrade....it just isn't worth it. Although...I will admit...if I'm going to risk Y on a transcon...this is one thing US does have the rest of the industry beat...row 22 on an A321.
That is one thing I LOVE about CO...I can book the lowest fare, with miles...and I don't have to worry about it...for those times when I want to save a sheckle or two and not pay.
My rock star Professional Travel Manager just saved my sorry butt $900 sheckles and booked me PVD-STT-PVD for $453 + 30,000 miles...
WELL worth it.