I know that magicians and card sharks can 'force' you to choose the card they want you to choose, but I am wondering how a person can get past the gate and onto the aircraft without having their ticket scanned and passport checked - no matter how carefully they might be watching people's eyes?
Unless they used fake documents that somehow look genuine to the computer scanner. Hard to see how a person in the queue who does not produce any documents would be allowed past.
Are there airports where these documents are not always checked at the gate? (probably best not to be too specific !).