Originally Posted by
IAH-OIL-TRASH
UA is required sometimes to make a good faith effort to check visas, but they don't go into detail of them beyond a minimal scan - usually of the validity dates and country. UA can't verify the actual validity of a visa beyond a superficial check (UA puts that on the passenger) - and UA does assume the risk that the destination authorities may put a passenger back on a return flight.
IME (as detailed elsewhere) UA does not even do a minimal scan, as the GAs missed my expired passport and permitted me to board an international flight. Thankfully I was not deported on arrival due to the discretion of the Dutch immigration service. Of course, most are not so fortunate, particularly in Japan.