Yikes. What happens when you have been standing in a 2 hour line, and finally get to the checkpoint? Your face might not be so happy. How about adding that you’re flying to a relative’s funeral?
Who knew how prescient ‘1984’ would be?
Yeesh, people... this is NOT about looking for happy or unhappy people. It's about reading people. We all do it to one extent or another. Sometimes you can tell that somebody's mannerisms, expressions, personality... just doesn't fit right with who they are, what they're doing or what's going on around them...
It's not mind reading or thought police. It's seeing somebody in the line or in the waiting area that seems to have a different plan than everybody else getting on that plane.