mikeymikey is absolutely right on the money. Your ability to check a rod tube depends on the aircraft being used.
Twinjets like 737s, 757s, A319s and such can swallow canoes in their cargo holds, never mind rod tubes. The problem comes when you have to fly on a small regional jet or a turboprop, since most of those were designed for business travel and can't handle anything bigger than one overnight bag for each passenger.
If you're going to a small town in NW Ontario on a scheduled flight, you will almost certainly be in a small turboprop like a Saab 300 series, a Beechcraft 1900 or maybe a Convair 560, and none of those will take a tube much over four feet in length. You better call the airline ahead of time and confirm what kind of plane you're on, and what size tube it can accommodate. Otherwise, you might have to leave your rods behind. (That happened to me on my first trip to Kesagami. Air Ontario couldn't fit my rod tube on their Beech 1900, so my rods spent a week in storage at Pearson Airport. Of course they only told me this after I arrived in Cochrane and the rods didn't appear. Thankfully, I bumped into Bruce Leeson at the lodge, and he was kind enough to loan me a couple of his outfits for the week. Thanks again, Bruce!).
You can fit large rod tubes on small float planes (Cessnas, Beavers) by running them down the floor under the seats, but they won't do that on scheduled commercial flights. Having worked for a couple of TV fishing shows and a few fishing magazines since the early 1980s, I've taken hundreds of flights with rod tubes, and on just about every type of plane imaginable. Trust me, don't leave anything to chance. Call the airline and confirm exactly what they can handle.