Firearms can easily be transported when flying, but they must be unloaded and locked in your locked checked baggage. Have flown all over Canada and US with firearms and in many cases it's faster going through check-in than for normal passengers. In Toronto, when flying Air Canada with firearms you check-in at their special services counter (and usually avoid most of the lineups). Sign the statement form that the firearms are locked and unloaded... you're good to go. Just keep in mind that ammunition must be separate from the firearm... and airlines like to put a big sticker on the outside of your luggage announcing "AMMUNITION" so I usually don't take ammo. There is no requirement to put a sticker on outside of luggage for just the firearm... in fact in the US they passed a Federal law prohibiting the airlines from putting the "Red Tag" on luggage containing firearms... go figure, they had too many firearms being stolen from the luggage

. Now they put the red tag inside the luggage or simply don't bother with the tag.
Mark