Jedi,
There is a serious current shortage of Air Traffic Controllers in Australia. The reason behind the current international recruitment campaign. Something that hasn't been seen in Australia for 20 years. When an Air Traffic Service provider starts recruiting controllers from overseas, it means that the responsible managers have stuffed up their forward planning for staffing to the point where the domestic recruiting and training part of the business cannot provide enough trained controllers to replace those who are leaving the operational environment.
The managers were warned about the looming shortage and were inadequate in their actions (or lack there-of) to rectify the problem. In some cases, certain managers stated aggressively that there was no problem.
It's important to note that it is cheaper to run a roster (approx 15 controllers working the same sectors grouped into a small business unit) with one or two lines of overtime rather than employ the required number of controllers on a full salary and leave entitlement. That way, the manager can demonstrate an efficiency in that financial year and guarantee full payment of his performance bonus. It could be debated that such actions are motivated by personal greed and a belief in one's infallibility of decision-making. Such a belief can result in resentment of the manager by his/her subordinates.
The contingency for unexpectantly losing a controller from an operational group was the transfer of a controller from another operational group into the group that was one-too-many controllers below it's minimum requirement. The point at which there are physically no more controllers on a day off who can be called to attend.
The problem with this is that a point was reached where most of the groups were operating one or two controllers short and therefore... no contingency.