They do anyway, you can change the death weapon entry however to include a bigger blast, and you can change the particle effects associated with it. Just rummage in the aircraft entries, you'll find what you need.
Couldn't you use the VehicleCrashesIntoBuildingWeapon= and VehicleCrashesIntoNonBuildingWeapon= flags in the PhysicsBehavior module to have aircraft explode on impact?
from my experience...if they crash into an object before hitting the ground they just disappear in thin air like GuyInTheWindow said....even with high detail... If they touch the ground without colliding however, they do vanish in a fireball