You can do it with a trigger.
Name the plane and put the condition of the trigger as;
!(Alive PlaneName)
Activation as;
bomb1 = "laserguidedbomb" camcreate (Getpos PlaneName); bomb2 = "laserguidedbomb" camcreate (Getpos PlaneName)
This way when the plane dies it will explode in a giant explosion. Either on the ground or in the air. Notice you need to create two bombs since if the plane dies in mid air the two bombs will collide and explode, otherwise one would just fall to the floor. This way the plane will explode mid air. And on the ground, its going to make one heck of a booom.