Are you talking about landing lights or nav/beacon/strobes? For any landing or taxi lights that are behind the cockpit, their beams must be pointed slightly outward and/or down from the aircraft center line so that they don't shine inside. Until LM adds shadow casting to dynamic lights, this is the only solution I've seen or been able to implement.
For any other lights, changing the effect radii for their various particles/emitters in the .FX file should limit the distance at which lights illuminate other surfaces. Try cutting the radius in half and see if it behaves the way you want it to.