Originally Posted by
TRRed
The instructions on the app say to scan the "front" of your passport. Apparently what they should say is to scan the main page. Some of the comments on this thread helped me figure that out.
Do you have an exact full quote or did you take a screenshot of it? Perhaps a call to United could clarify. I also have to think twice when customs asks you to wait "behind the line", which to me is really in front of the line.