I visited the Willis Tower just after opening at 9am, and there was already a sizeable queue. There is a dedicated line for City and Fast Pass visitors. The regular admission line had waiting times of 30 minutes, but it didn't take that long. As security is in place, jackets need to be removed and any small items need to be placed in a bag or your jacket. Once at the top of the Tower, the views are incredible. There are extended viewing booths where you can have your picture taken or take your own pictures, but I didn't bother as the queues were too long.