There are two things I would say.
First of all, a single controller working doesn't in and of itself present a safety risk, necessarily; however, in a system that depends on redundancy to ensure safety, we feel it's important that, as in other equipment areas, this redundancy should occur in staffing as well. If someone is working alone and something happens and they need some additional help, there's no one else there. No help is coming. For the system overall, I think there's a challenge there with respect to resilience.
If someone calls in sick, as happened recently in Hamilton.... There was a single controller scheduled for a 12-hour shift. He was ill, and the tower had no choice but to close. That's obviously not a situation that we want to see.
The simple solution is that we need some more people. When you have more staff, there's a little more resilience to the operation, and from a safety perspective, in the event that something happens, that person has additional help.
In addition to that, on occasion a controller needs to be relieved if something serious happens. Perhaps he's made a mistake or some sort of incident has occurred. That person is supposed to be relieved from duty. If there's no relief, it makes it difficult for the company and the employee to handle that situation.