Originally Posted by
bmwe92fan
That's my thick skull - and I thought it was relevant having just returned from a flight to Frankfurt where after arrival i flew to Denmark and took a train to Sweden and no one ever checked my passport after arrival in FRA - in spite of entering two new countries - quite different than the USA - which to me is likely what op is used to....
It's called Schengen. For purposes of border crossing, you were within what amounts to one country. That's not the case elsewhere.
And, it has zippo to do with OP's situation.
The bottom line is that both Singapore and Canada would fine UA if OP showed up without proper docs. So, UA checks the docs. It's that simple and actually had zippo to do with US border and transit law.