I was kind of thinking that simple planes needs blimps and similar stuff so like balloon blocks so you can make blimps and airships

Another was making underwater so you can explore it

Parachute blocks so you can make parachute drops, slow your drag car etc

Maybe making "couplers so you could couple up and tow a plane or make something similar

And a small city too maybe with Ai cars there and maybe airports with Ai traffic