A pilots' union has said "more needs to be done" to tackle the growing use of lasers against aircraft after a New York-bound plane had to turn back to Heathrow.
The Virgin Atlantic flight returned to the west London airport as a "precautionary measure" after the co-pilot reported feeling unwell following the incident on Sunday.
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A Virgin Atlantic spokeswoman said the safety of the crew and customers on board the VS025 travelling from London Heathrow to New York JFK flight was a "top priority."
They added: "All customers will be offered overnight accommodation and we will get them on their journey as soon as possible. We are working with the authorities to identify the source of the laser that caused the return of the aircraft to Heathrow."
Police said they were trying to find the source of the beam.
In 2010 a law was passed in the UK which allows offenders to be charged with "shining a light at an aircraft in flight so as to dazzle or distract the pilot".
If the distraction or dazzle is serious, a person may be found guilty of "reckless endangerment" and sent to prison.
According to the British Airline Pilots Association (Balpa), a laser can result in temporary vision loss associated with flash blindness, a "visual interference that persists after the source of illumination has been removed", an after-image, an "image left in the visual field after exposure to a bright light", and glare.
Balpa general secretary Jim McAuslan said: "This is not an isolated incident. Aircraft are attacked with lasers at an alarming rate and with lasers with ever-increasing strength.
"It is an incredibly dangerous thing to do. Shining a laser at an aircraft puts that aircraft, its crew and all the passengers on board at completely unnecessary risk.
"Modern lasers have the power to blind, and certainly to act as a huge distraction and to dazzle the pilots during critical phases of flight."
He added: "We repeat our call to the Government to classify lasers as offensive weapons which would give the police more power to arrest people for possessing them if they had no good reason to have them. This incident shows why this is becoming more and more urgent."
Between 2009 and June 2015 more than 8,998 laser incidents across the country were reported to the UK Civil Aviation Authority.
Topping the list for the number of most frequent laser incidents for the first six months of last year was London Heathrow with 48, followed by Birmingham with 32, Leeds Bradford with 24 and Manchester with 23.
A CAA spokesman told the Press Association: "Shining a laser at an aircraft in flight could pose a serious safety risk and it is a criminal offence to do so. We strongly urge anyone who sees a laser being used at night in the vicinity of an airport to contact the police immediately."
In November 2015 it was reported that the eye of a British Airways pilot was damaged by a "military" strength laser which had been shone into the cockpit of his aircraft earlier in the year.
It is understood that the Virgin Atlantic aircraft, one of the latest flights to be affected by a laser, had passed over the west coast of Ireland before heading back to Heathrow.
A message on Virgin Atlantic's status website said: "Following this incident the First Officer reported feeling unwell. The decision was taken by both pilots to return to Heathrow rather than continue the transatlantic crossing."
It is understood that there were 252 passengers and 15 crew on board the flight.
A Metropolitan Police spokesman said: "Police were contacted at approximately 9.35pm on Sunday February 14 following reports of a laser shone in the direction of a commercial flight that had taken off from Heathrow Airport.
"Inquiries continue to establish where the offence took place. There have been no arrests."