If this game is still being developed, and the developers read these pages, I think it would be a good idea to notify the player when they get access to a new category of planes. I have access to cat 3 but have no clue when this happened. It's only just occurred to me that you don't have to do the task in the plane they give you at the start.
I think the game's unbelievably engaging early on, but does get less and less so as you progress. I think a military version could give much more scope in terms of missions being more varied, and progressively more difficult as you move up the levels. You could have spy planes for recon, bombers for taking out bridges and power plants etc, fighters for intercepting enemy bombers, and helicopters for dropping troops in strategic positions behind enemy lines. Appreciate these things are easy to envisage and much harder to implement, but the biggest flaw with eurofly is its lack of variety, and the fact it gets easier rather than harder.
By the way, I noticed early on in the other eurofly thread, the devs were asking for native English rewrites of their text. I did the quick start and sent it to the email the guy posted. It was a few days ago, but have had no reply. Maybe he doesn't work on the project anymore, or the rewirite was pants. Anyway, it's there if you want it. I'm doing the task briefings too, but that's for my own satisfaction. If the devs want those when I'm done, and they read this, let me know.