Laser lights being flashed at planes is a growing concern for pilots, including those who fly in and out of Changi Airport.

They appear harmless but laser pointers can cause temporary blindness, which is especially dangerous during take-off and landing.

Between January and November last year, the Civil Aviation Authority of Singapore (CAAS) received 53 reports of laser lights being flashed here, compared with 28 for the whole of 2015.

Worldwide, the number of incidents has jumped from one a day in 2008 to 17 in 2012, which is more than 6,200 a year.

Recent data is not available but the industry estimates that the figure has easily doubled in the last four years.

LASER STRIKES In Singapore, first-time offenders can be fined up to $20,000 Subsequent convictions carry a maximum penalty of a $40,000 fine and a jail term of up to 15 months

While such acts have not caused any serious mishaps yet, the numbers are alarming, said pilots and airlines.

Mr Loo Chee Beng, CAAS' director of air navigation services policy and planning, said: "A laser light shone into an aircraft cockpit can confuse, distract or cause discomfort to the pilots."

In more severe cases, pilots may experience temporary flash blindness, and even suffer from eye injuries leading to incapacitation.

"These effects are significant hazards to flight operations and put lives at risk, especially during the critical phases of flight, that is, during take-off and landing," Mr Loo said.

Laser pointers, commonly used during meetings or presentations, typically emit a red, green or blue light.

Even at a very low power of 5 milliwatts (mW), the pen-like battery-operated devices can cause temporary flash blindness in pilots if aimed directly at the eye - even from the ground.

Singapore Airlines (SIA) spokesman Nicholas Ionides said that in such situations, pilots are trained to follow procedures such as looking away from the source and shielding their eyes, alerting other crew members and handing over control of the aircraft to somebody else.

The International Federation of Air Line Pilots' Associations (Ifalpa) said such attacks are frequently the result of deliberate action. "This is either because the perpetrator has a lack of understanding of the consequences, or of more concern, the perpetrator understands the hazards of lasers and illuminates aircraft with the intent of doing harm," it added.

The association is "deeply concerned at the alarming increase in laser strike incidences" and wants such acts to be classified as unlawful, added Ifalpa's acting president, Captain Ron Abel.

A proposal, supported by other industry players, including the International Air Transport Association (Iata), has been submitted to the International Civil Aviation Organisation (ICAO) - the commercial aviation arm of the United Nations.

In Singapore, where there are already penalties against such acts, first-time offenders can be fined up to $20,000.

In the case of a subsequent conviction, offenders face a maximum penalty of a $40,000 fine and a jail term of up to 15 months.

The Straits Times understands that so far no one has been prosecuted.