In my opinion, it is noise. I can't see it in the full images, but it's very visible in the 100% crops. I did notice that the photo was underexposed by nearly a full stop. In theory, that would make the noise a little worse, but I don't have any data to show whether that's the case or not.
I am headed to an airshow later today, so I'll see if I can duplicate the scenario.
I did not notice I had set exposure compensation.
Well spotted, that probably explains a lot.
That said. I'm wondering if the temperature of the camera itself has anything to do with noise? The sun was on the camera at times throughout the day and did sometimes feel quite hot/warm.