I flew to Atlanta Georgia in the Spring. This is my experience: I put my pistols, trigger-locked, in a plactic case (Not a pelican, only because I'm poor, but pelican-like) and padlocked. I put my ammo in a cheapo small plastic pistol box. Like the kind they used to sell at Walmart: holds a single pistol. Just took the foam out. Locked the little box with a cheapo small luggage combo lock. I put this little case in my regular luggage, NOT in the pistol luggage. Of course I had my BATF form 6, my Alaskan small game license, and a letter from the competition I was going to, on me, in a folder, easily accessible. When I showed up at the airline check-in counter, I told them "I need to fill out a firearms declaration form". Basically it's just a short letter that you sign, saying that your guns are unloaded and that the ammunition is not loose. Yes, make sure your ammo is in neat boxes, and not dumped in a bag or whatever. Then for some strange reason, they made me put the form INSIDE the case with the pistols. So at the check-in counter, I had to open my gun case, at least enough to shove the paper in. Then they walked me and my luggage over to US customs at Pearson airport. The US customs guy was only interested in my BATF form. He takes it away for awhile, ostensibly checking it out, when he came back, he wanted me to open my pistol case and he checked the serial numbers against what the BATF form says. I can't remember if he wanted to see the ammo. I don't think he did. When he was satisfied, he let me lock up all my stuff again and sent me on to the luggage scanning area. Which is staffed by local security. Of course THEY were fascinated by my pistol luggage and wanted me to open it so they could inspect it (before sending it through the X-ray machine actually...). So it was a pain in the ass, but I unlocked it again, and took out the pistols one-by-one to show them they weren't loaded. (now in a fairly public area by the way) When that was done, I packed them up again. I don't think they were all that interested in looking at my ammo either. There was a sticker that the airline put on my case, which is supposed to be some secret code for "GUNS & AMMO IN HERE!!!" that was falling off, because I had armor-alled the case first (Hey! I might not have a fancy case, but I like to take care of it!) and one of the nice security guards gave me some clear packing tape to tape it on. But of course, being in an airport, neither me, nor the guards had any kind of knife to cut it, so one of them just kept winding and winding and winding the tape around my case until the roll was done. Kinda annoying, but I wasn't going to give him any grief. Then my luggage was on the carousel and away it went until I picked them up in Atlanta.
Coming back to Canada, the process is somewhat similar. You turn up at the check-in counter and say "I need to fill out a firearms declaration form". You sign the paper, they take you to the 'oversize luggage" screening area. They x-ray the luggage and I think they asked a few questions but didn't open anything. Then off it went until landing in Toronto. Now coming back into Canada, you have to fill out a customs declaration form. "You bringing in fruits? Plants? Booze?" etc. And of course, there's a tick-box for firearms. So I ticked "yes" for the first time in my life. When I landed, I collected my luggage and had a bit of a heart-stopping moment. There was a sticker on my gun case, saying that my luggage had been opened and inspected. But my lock was still intact, so either it's such a common combo lock that they knew the combination to, or they could open the case enough on the non-lock side (on subsequent flights, I now double lock) and look in. The small luggage lock on my duffle bag (which had my clothes and ammo) was cut off, and the small luggage lock on the pistol case inside was also cut off. So despite being X-rayed at Atlanta, somewhere along the way, there was still further inspection. You then drag your stuff to the first Customs line and the guy looks at the "YES" tick beside the firearms question and sends you off to the big Customs hall. This is the place where people who are immigrating to Canada are sent to, with their million pieces of luggage. So expect to stand in line quite a while, with screaming third-world-like children running around screaming, and customs officials trying to ask questions to people who do not speak either official language. Finally I make it to one of the tables, the guy looks at my customs form, and wants to see my paperwork. He looked at me incredulously and asked "Are YOU an Air Marshal!?!" (I'm a kinda short, kinda fat, 30-40-something, glass-wearing guy). No. Of course not. Just a sport shooter. He says he figured so, cuz then I'd have a different passport. At this point you hand him your ATT, your RPAL and copies of the registration certificates for good measure. He then wanders off for awhile. Maybe people are looking at you through the big one-way mirror wall. Maybe not. I don't know. But he wasn't gone long, came back and said "You're good to go". and then he said "Doesn't take long when all your paperwork is in order, eh?". Well, this is the only way I have ever travelled, so I didn't really have anything to gauge this against, so my only reply was a cheerful "Yeah! Thanks! Have a good day!" Gathered my luggage up and got out of there.
So it's totally do-able and not that hard if you follow common sense and have your paperwork in order.
Tips:
-You said you had your BATF form 6 accepted. Good. Did you also contact the Ontario CFO and get an ATT to leave the country? The ATT will be good for a year, or at least for the same length of time your BATF form is good for. AND they want to know which border crossings you MIGHT be using. So for good measure, I rattled off all the land border crossings I could think of and Pearson airport.
-The airline regs say your firearms and ammo must be packed "separately" but what do they mean? In totally separate pieces of luggage? Or could my ammo be in a small box inside the same case as the firearms? I don't want to argue this point with whoever is on the desk that day, so I just pack them in separate pieces of luggage. I've flown 6 times this way so far, and it's all been good.
-Have your paperwork organized! For the US people, I stapled a copies of the BATF form, the Alaska hunting license and for good measure the letter from the match I was going to together and just handed them the whole package. (Being paranoid, I also kept the originals in the folder with me.) For the Canadian people, I stapled a copy of my ATT and registration certificates together.
So far, my experiences have been good. Knock on wood...