Your Exif data shows f/5, 1/1000, ISO 100, 105mm. You can clearly see the motion blur on the front of the wings and horizontal stabilizer (especially via my second version, cropped and scaled up a bit over 200%). I say 70% of the sharpness “loss” of this shot, is that you needed to peg your shutter speed at 1/4000, and close the lens to f/6.3 (given my experience with that lens, on a 1D Mk4). This would have required ISO 640 or so, which would have been fine. The other 30% of sharpness loss, is the glass of your windshield, and a slight lack of the lens’ sharpness. It’s not a fault of the AF, in my opinion…although it’s possible it might need some tweaking in AFMA? I have no idea. Not sure if you were in servo AF mode or not, either…that can be a big factor…can help at times, other times not. I probably would have multi-half-pressed the shutter in single shot AF as the plane got close, then held it half pressed til it got close enough. Center point only, of course…then recompose as necessary as you are panning, etc.
You also likey didn’t pan with the plane quite fast enough as it passed…not easy to do, I know. Also, if you left image stabilization on (you probably did not)…that would have been a big no-no with this lens…as it has no panning mode. I think the image would have been a lot more blurred if it had been left on. If it was on, then you must have done little or no panning. I can only guess.
I converted this jpg to a DNG, so I could first open in ACR, then crop it farther, then play with it. I added 33 on the sharpening slider with .5 pixel radius, then pushed to 92 on the detail slider. I then saved changes, and opened the image in Photoshop. Then I took a 10 hour nap after my daily afternoon romp with a room full of cheerleaders (hey somebody laugh!)…nah I did all this in a few minutes.
In PS, for the second image, I scaled it up 2.2x in “bilinear”, performed no other changes, saved as jpg. This should illustrate my point about the motion blur (wing and stabi leading edges…even the line around the door on the side). At a closure speed of approximately 1200 mph…you need more than 1/1000/sec shutter speed. Frankly, I’m surprised it’s not any more blurred than it is! Obviously you panned somewhat. MORE THAN A DECENT JOB for an admitted “amateur”.
Sharpening artifacts around the high contrast edges as metal meets sky? Yes, but it’s not all that bothersome. Look good with this amount of crop on a billboard the size of a 2 mile runway? Sure, why not…:P !!!