Upload & Sell: On
Also it was my first outing with my new 500mm F4L II - I have realised I'm in for a very steep learning curve! I tried all combinations of handheld (7D, 5D3, =/- 1.4x converter. It obviously needs to be mounted on a gimbal with a heavyweight tripod (I have a gimbal, but only a lightweight carbon fibre tripod!!).
I can't say much about tripods since I don't use them often, and thankfully followed someone's good advice to buy a good one the first time around. I'm partial to RRS over Gitzo, and that's about all I can tell you that might be useful. But they're both expensive, and there are certainly other options that should give you a good tripod for a much lower cost.
I would recommend sticking to handheld, though. There's just too much radical change in direction -- and in two dimensions no less -- when shooting aviation, and it's bloody hard to rotate yourself and the camera around the tripod's support point in order to pan. Physically hard to do quickly and steadily, not just hard to learn. My suggestion is first to try to do everything you can with this lens, handheld, before contemplating a tripod for aviation use. A few more outings with it may improve your technique a great deal, and a little work on your core, your balance, and your arm/shoulder strength will all go a long way.
Then, if you really find it's too heavy after doing this, you'll have to choose between the limitations of a tripod and gimbal or simply using a lighter kit. You might want the 500 for birding or something else, and so might prefer to stick with the tripod. But if aviation is your primary goal, then a 100-400might be a better lens for you, even though it's shorter and doesn't have quite the same IQ, if its more compact frame and lighter weight mean you can use it more effectively.
Love the Swordfish, by the way!