My first office job was hourly, and paid overtime. For a short time, there was so much work we were allowed to do as much overtime as we liked. After a while we were told no overtime without permission, and then we were all changed (ostensibly) to exempt and salaried, but nobody said anything about us being "managers".

Now I am salaried, and am not allowed to put in overtime on my own initiative, but I am eligible for it if requested. The next salary grade up, union rules allow unpaid overtime.