In fact, don't take my word for it; check this out:  LaserPointerSafety.com

Another problem is that the beam is much larger at long distances than you might think. Even though the laser projects a small, millimeter-sized dot close up, at longer distances the beam can be many inches across. When the beam hits the windscreen of a cockpit, or the bubble of a helicopter, imperfections in and on the glass spread the light out even more:

Laser light in the pilot's eyes causes glare (inability to see past the light). At higher power levels, it can also cause temporary flashblindness and afterimages (like when you look at a bright camera flash, and cannot see for a many seconds afterwards). Since the beam can't be held completely steady on the cockpit, pilots experience one or more of these bright flashes:

To make things even worse, a pilot being targeted may also be worried about eye damage and eye injuries, and the possibility of the laser being an aiming device on a weapon. A worried pilot is a distracted pilot -- not a good thing during critical flight phases such as landings, takeoffs and emergency maneuvers.

For all these reasons -- and especially due to the distraction, glare and flashblindness effects -- you should NEVER point a laser towards an aircraft. (It is not even smart to aim directly at stars, since a slow-moving far-away aircraft could look like a star. Instead, if you are pointing out stars at night to others, circle the star as described on the Tips for outdoor use page.)

There are pictures that illustrate the dangers.