I've had no problem signaling planes using a simple mirror and the two-handed aiming method. I think it comes down to the fact that when you wiggle the mirror even a little you are actually moving the signal a large distance out where the plane is (just consider the geometry) and in additon, it is not a laser and and the beam does expand a modest amount as you get a mile or more out. Again, the true test is the real world and it's worked fine in many tests with real airplanes.