Shane in a head on collision both planes will collide at the same time no mater what the lag is.
I.E. you are always see the other plane at (your lag + other players lag ) time ago. So total lag at seeing the plane is = for both, and hence they both would see the collision at the same time.
The only advantage the greater lag player has is if both planes do collided, and both planes suffer a death in the collision. The slower lag player would be awarded the kill. But both would still end up dead.
HiTech