The air assets don't stay at the base at all times. For instance, we have F-18s sometimes at Uplands airport here in Ottawa; they deploy to different locations around Canada. It's a matter of making sure they're on location when a threat arises or when it's thought that there might be a potential threat. For example, during the Vancouver Olympics, I don't know for sure, but my guess is that the F-18s were deployed closer to all the activities.
On April 12th, 2016. See this statement in context.