Originally Posted by
findark
UA will perform the document validity check at the point of first check-in. It's quite possible that OP was the only American in AUS going to Japan that day, and even more likely the only one on that flight departing AUS.
Yea, that's part of the problem, I think most airlines do, to avoid a first flight in vain. There should be a visa re-check at the international hub for those passengers connecting there...