Originally Posted by rknicker

When you enter ORD, go all the way to the left or right. To the left there is a full size security screening area there that is typically empty (typically opens around 6am), even when hundreds of people are lined up at the other checkpoints. On the far right, where Lufthansa used to be I believe, is a small checkpoint that is also shorter. If you fail pre-check, head left, it's no more than a 2 minute walk and the line will be shorter.