What we have now is chopper/plane exploding after hitting the ground on high speed. It would look better and would be more realistic if plane/choppers would crash to the ground kicking up ground and dust particles up in the air rather than exploding in the hollywood-style.
At least exploding should happen much more rare.
watch 0:48 http://www.youtube.com/watch?v=88F-HGfVHrU
watch 0:48 http://www.youtube.com/watch?v=88F-HGfVHrU
I propose to use some dust and ground particles along with the debris flying caused by the hit to ground. There could be some fire and smoke - but explosion looks way too unnaturally and exaggerated.
Also when helicopter crash, there could be dust and debris flying just a little bit longer till the engine/rotor completely stops working.
As for destroyed models of aircraft I would propose more detailed predefined ones rather than ones with darkened textures.
In most cases planes don't explode when hitting the ground - fire is caused by ignition of jet fuel.