Why Lasers Are So Dangerous to Airplane Pilots

— -- After a spate of commercial planes flying over New York and New Jersey reported spotting lasers beamed toward their aircraft in recent weeks, the FBI and Federal Aviation Administration are investigating what one agent called a laser "assault."

They may not yet know where the lasers originated – but they do know this isn’t a one-time problem.

Last year, the FAA reported 3,894 laser events nationwide – and pilots have already experienced more than 2,750 laser incidents this year.

Pointing a laser into a cockpit is a federal crime, with a potential five-year prison sentence and $250,000 fine. So why are so many people doing it? And how dangerous are these incidents, really?

We asked ABC’s aviation consultant and airplane pilot John Nance:

What happens to the pilot when somebody aims a laser at the cockpit?

It's a sudden flash that can flash-blind you to the point that you can't really see what you're doing. If it gets both eyes, which is possible, the pilot’s going to be fairly well out of the loop.

What’s the worst-case scenario?

Our nightmare scenario here is getting a pilot – either one or two pilots, however many there are in the cockpit – so flash-blinded that he or she can't land the airplane, can't even see to fly it. You wouldn't think of a little green laser as having the power to bring down an airplane full of people, but if you get the eyes of pilots flash-blinded at the wrong moment, you can do that – and you could end up killing 400 people.

Even if the plane lands safely, can the lasers hurt the pilot?

The potential for getting hit by one of these lasers and ending up with permanent eye damage, I'm afraid, is very high. If you happen to linger on it for just a couple of microseconds, that might be enough to completely wreck your retina. That could put a pilot out of the business of flying.

Why the hubbub over green lasers in particular?

The green lasers are much more powerful than the red lasers that we've used as pointers in speeches and so on for a long time. (And for entertaining our cats.) The green lasers are serious things. And this is one of the problems, that they 're out in the public without the public understanding the lethality if they're used wrongly.

Is there anything we can do to protect pilots?

If I’m flying a plane and I see a laser being shined around, the first thing I'm going to do is to try to turn away from it because I don't want to run any risk that they might actually illuminate my eyes. But we don't have any way of defending eyeballs of pilots against these things because they travel at the speed of light.

Why are so many people shining lasers at airplanes?

Number one, there are too many of these lasers that have been sold indiscriminately –with no warnings on them. And Number two, we've got a lot of very ignorant people out there who don't seem to understand the danger of pointing that at an airplane. People are throwing them around in the air indiscriminately.

What can happen to people misuse lasers?

I really can't emphasize enough how serious a federal crime this is, and I guarantee you, the FBI's going to be pulling out all the stops to find anybody who tries to shine a laser at a cockpit.

ABC News’ Matt Hosford, David Kerley, Josh Margolin, Aaron Katersky, Katherine Faulders and Devin Dwyer contributed to this report.