I posted this video once before, but I think it's relevant to this discussion:
There are two collisions in this video. The first is a midair between a Bf-110 and a Spitfire, in which the Bf-110's wing is cleanly severed, while the Spitfire very unrealistically takes only light damage. The second collision is when that Spitfire bellies into the ground, and the right wing is removed along a very jagged looking break.
I'm thinking the code for severing wings in flight must differ from the code for losing wings to collision with the ground and/or static objects.