In Nunavut, for example, it's exclusively air travel between communities and for connections to the south. Of course, there's the marine supply.
I gather your question is more about the private use of aircraft instead of a vehicle.
I can't comment on what the numbers might be. Obviously, the population of Alaska is a little different from that of any one of the collectivity of territories, but there's no doubt that air is absolutely critical for getting around. It's the same in the Yukon. You see the air mode being used around exploration and mining, and so on. It's the same thing in the NWT. Air is fairly similar across the territories, from the point of view of how it's used. It's complemented by other modes, depending on the territory you're looking at. It's very much a critical mode for all three territories, and more critical as you go farther east.