I do not know a thing about the messages. If your computer detects your plane intersected with another object, your computer assigns the appropriate damage to your plane.
If the other players computer detects his plane has intersected with another object, then his plane will be assigned the appropriate damage by his computer.
Basically, the same rule applies to every plane in the game. The computer assigns the damage to the plane the player is flying, when it is needed.
The confusion comes in due to the differences in how each computers plane is in a slightly different location in its virtual world, as compared to any other computer. Without this, then if one plane collided with another, the other would also collide as well.