Lasers in the hands of kids or pranksters are becoming an increasing concern to pilots using Honolulu airport, with one federal official warning that the devices could impair a pilot’s vision during critical takeoffs or landings.

The Federal Aviation Administration said there were three incidents of laser strikes on airliners here on Dec. 24, four more on New Year’s Eve, and two on Sunday.

All together, there were 45 instances of laser contact reported by pilots in 2010 compared to 21 the year before, with Honolulu ranked eighth in the nation for the worrisome actions, said Ian Gregor, an FAA spokesman for the Western Pacific Region.

On the same day about a year ago, pilots on three airlines — Alaska, Northwest and Hawaiian — reported green laser strikes on their cockpit windshields about six miles northeast of Honolulu Airport.

A pilot on the Alaska Airlines flight experienced a momentary blur in vision, the FAA said.

The airline laser aiming here is part of a steep increase around the country, with about 300 laser contacts reported in 2005, 1,500 in 2009 and 2,800 in 2010, Gregor said.

"The FAA takes these incidents very seriously because of the potential safety hazards they pose," he said. "Lasers can distract pilots or even cause temporary vision problems when they are on critical takeoff or landing phases of flight."

There have been no crashes related to the strikes, he noted, but the increase in targeting using green lasers is a concern. Experts say the trend may be due in part to technology advances and, often, simple ignorance.

Inexpensive yet powerful handheld lasers have become widely available, with abuse following closely behind.

Greg Makhov, president of Lighting Systems Design Inc. in Orlando, Fla., who has worked with lasers for more than three decades and teaches laser safety, said a 5-milliwatt-output laser pointer cost hundreds of dollars in the mid- to late 1990s.

A check of Amazon.com shows that a 100-milliwatt green laser "pointer pen" can be had today for just $20.98.

"They’re so cheap that people consider them toys," Makhov said. "They give them to kids and of course, kids don’t understand that that 20 milliwatts reaches out into the sky maybe a half-mile — and now you’ve got a problem."

When people are caught aiming a laser at an airplane, the reasons given for doing so run the gamut, he said.

"You have people who say, ‘I was being stupid,’" Makhov said. "Sometimes it’s malicious. I know of one case where it was reported that somebody was particularly annoyed at police helicopters flying overhead, creating noise and waking them up. This was his attempt to respond to what he felt was an intrusion on him — not a very good response."

According to the website LaserPointerSafety.com, run by Patrick Murphy, executive director of the International Laser Display Association, a laser pointed into the nighttime sky can appear to end after a certain point, and a person might aim it at a plane thinking the beam won’t reach the aircraft.

In reality, a 5-milliwatt green laser — the maximum output for any device labeled and sold as an office laser pointer — is a distraction to pilots two miles away, according to the site. A 125-milliwatt laser can cause a cockpit distraction more than 11 miles away.

The beam spreads out the farther it goes, and a pilot may see something akin to a flashlight or searchlight. Because it’s hard to focus on a plane, the light may momentarily play across a cockpit, and the pilot would see flashes, according to the laser safety site.

"The flashes are distracting at best, and at worse, they can be bright enough to cause temporary flash blindness," the website said.

There have been arrests around the country for interfering with flights. The FAA’s Gregor said in his region, people have been caught in the past few months in several California cities and the Phoenix area.

He’s not aware of any Honolulu arrests, but that doesn’t mean HPD isn’t trying.

Early on New Year’s Eve, police were dispatched to the Hawaii Prince Hotel for a report of an airliner being laser-targeted, but no one was found.

Makhov, with Lighting Systems Design, said if a red laser pointer of 5 milliwatts or less accidentally sweeps across a person’s eye in an office setting, the chance of injury is "pretty much negligible."

A green laser, which has a smaller and more energetic wavelength, can scale up to much higher power, and the eye is much more sensitive to the green light than red or blue, he said.

The New England Journal of Medicine reported in September that a 15-year-old Swiss boy bought a 150-milliwatt green laser on the Internet and during a "laser show" with mirrors, swept the beam across his eyes several times, damaging his vision.

Murphy said it’s legal to own a laser of any power, but for it to be defined and sold as a "laser pointer," it has to be limited to 5 milliwatts or less.

"It’s one of those legalistic things where it’s so easy to get around it," he said. "You just don’t say (a higher-power device) is used for pointing or demonstration purposes."

Higher-power handheld lasers often are used and marketed for astronomy to point out stars, experts say.

Makhov said there have been reports of gangs in Los Angeles using lasers to ward off police helicopters. There has been no evidence that any laser use involving planes is terrorism-related, the FAA said.

The FAA’s Gregor said for the most part, astronomers are careful about the use of lasers.

But the increasing number of targeted aircraft shows that other people are not.

"You have to use these things responsibly," Gregor said. "Engaging in this irresponsible and dangerous behavior can get you arrested."