I would have to agree with the earlier poster - if you try to get there when they open (4:30) you may have a shot. If you try between 5:30 and 8:30, I'd say no chance. They are always booked solid and generally will not take walk-ups. I've been waiting in line to check in (yes, waiting in line to check in) and heard them turn away folks many times, and we always travel off-peak.