The fact that one airline operator at O'Hare had fallen asleep at the controls before does not mean that every operator should be disallowed from taking overtime. Overtime work for air traffic controllers in an important part of their economy. I think that supervisors should always keep a constant eye on their staff and ensure that their staff is well rested and alert. I think there should be guidelines for making controller take more breaks or be sent home at the disgression of the supervisor if they appear drowsy and not alert.
Both the operator and management are to blame. Overtime should be managed so that you have enough breaks and not too many hours - if needed, they should employ more staff. The operator should have also alerted others of his tiredness, as it caused a crash. The management should have been on high alert after this occurring before, and made sure that the specific person was limited on hours.
Given that the operator had past discipline for falling asleep, he should not have been allowed any overtime. Falling asleep in such a position is a serious problem and he should have been fired when it happened the first time. There are plenty of people who will take these positions and remain awake during any shift they're on.
No he shouldn't have been allowed to work as many hours as he had. Everyone's body needs a time to repair and refresh it's self. If you don't get that time you end up falling asleep and maybe endangering others lives. There should be a limit on how many hours one can work.