You've shown why the airshows I love drive me nuts.
The camera likes 18% gray (or, in your case, grey). So you got 18% grey. But it isn't what we want and we have to adjust.
The problem is especially delicate when you're following the aircraft during take-off or landing. The ratio of sky (blue, light grey, dark grey) vs. the ground (often green grass) in the image keeps changing as the aircraft climbs or descends. So the amount of EV compensation changes with each shot in the series. Ouch! I wish I had a bob for every AiF (Aircraft in Flight) shot I've mucked up owing to inappropriate EV compensation.
Never mind attempting to pan carefully enough - and keep focus tight.
Don't worry.
Find what works best for you.
Think about using raw+ so you've a bit more leeway on exposure for those images that you want to spend a couple of minutes on.
And keep shooting!