Directing lasers at a cockpit could have "devastating" consequences, leading eye specialists have said.
Handheld lasers which are pointed at a plane or a helicopter can "dazzle" pilots who "almost certainly will be distracted", they said.
If pilots are distracted at a critical time, such as during landing, the result could be disastrous, according to their editorial published in the British Journal of Ophthalmology.
The number of incidents of people pointing lasers at aircraft are on the increase, said Professor John Marshall of the Institute of Ophthalmology at University College London, John O'Hagan who is head of the Laser and Optical Radiation Dosimetry Group at Public Health England and John Tyrer, professor of optical instrumentation at Loughborough University.
In the UK there were more than 1,500 cases of lasers directed at aircraft in the last year, they say.
In February a Virgin Atlantic flight to New York JFK was forced to return to Heathrow as a "precautionary measure" after a laser was shone at the cockpit.
Just nine days later a British Airways service from Amsterdam was affected when a beam was aimed at the aircraft as it headed towards Heathrow.
But there is no evidence to suggest that lasers pointed at cockpits damage pilots' eyesight, the experts said.
There has only been one case of alleged retinal damage in a pilot as a result of laser targeting of aircraft, they said, but the "suspect" case is questionable because of the distances involved.
When the incidents occur the distance between the source of the laser is usually hundreds to thousands of metres. And the lasers also need to penetrate the cockpit windshield, but because these are usually scratched they would "scatter" the beam of the laser, they said.
"In this situation, the systems are operating over a long range - typically hundreds to thousands of metres and the laser beam has to pass through the atmosphere before traversing a cockpit canopy or windshield," they wrote.
"These are usually pitted or scratched and will serve to scatter the primary beam and may result in the generation of secondary and tertiary beams.
"In these situations, pilots tend to self-focus on a sudden bright light in the cockpit environment and may be dazzled, resulting in an after-image and almost certainly will be distracted.
"Obviously, if such a distraction occurs at a critical time such as during landing then the result could be devastating. Fortunately, these exposures are at irradiances that are incapable of producing irreversible retinal damage even at distances of 100m."
Between 500,000 and one million laser pointers, pens, and keyrings are thought to have been in circulation over the past decade, they said.
In the last eight years the "nature and supply" of handheld devices have changed dramatically.