I've travelled with a Bazooka Pro rod tube. It just counts as a checked bag and sometimes you have to go get it at a special oversize area instead of the carosel. These days I've heard some airlines have a surcharge for oversize items.
I have a 3 piece St Croix that I take whenever I travel. Never had a problem carrying it on.
If I were going to travel with a big rod tube again, I'd look into shipping it ahead. Less hassle, more confidence it'll acually get there and you can insure it.