A passenger on board a New York-bound plane which was turned back to Heathrow after a laser incident saw a pilot taken to hospital has described the ordeal as "scary".
The Virgin Atlantic flight returned to the west London airport when the co-pilot reported feeling unwell after a laser was directed at the plane as it took off on Sunday.
A spokeswoman for Virgin Atlantic confirmed the incident took place shortly after take-off and that the pilot was taken to hospital as a "precautionary measure", but was unable to offer further details on his condition.
She said the safety of the crew and customers on board flight VS025 from London Heathrow to New York JFK was a "top priority".
In a recording from the flight, a crew member can be heard telling air traffic control they have a "medical issue" with one of the pilots "after a laser incident on take-off", and that they are going to return to Heathrow.
Passenger Bethany McHutchinson told Sky News: "I think it's really scary, whether it was by accident or on purpose.
"If anything had happened, if it had been really serious, it could have put everyone's lives on the plane in danger."
She added: "It is very scary, especially when you are up in the air and hear stuff like that."
It is understood that there were 252 passengers and 15 crew on board the flight.
Laser expert John Tyrer, of Loughborough University, is a professor of optical instrumentation and has designed laser safety equipment for the police.
He said the pilot could have felt stunned or shocked by the incident, adding: "If you get an attack in your eye it will make your eye water and you may get a headache."
Mr Tyrer added: "If the laser is bought from reputable UK supply sources there are power density limits placed on these devices so that they can't cause any damage to the eye.
"However, there are people that buy these things off the internet which are shipped in typically from the Far East - which are very, very powerful lasers and have no use as a pointer."
In a bid to keep tabs on what is available online, as he continues to develop protective clothing against lasers, he said it is "very worrying" that powerful Class 3B and Class 4 lasers can be bought.
A Class 2 laser is usually advocated as suitable for a pointer in situations such as a presentation. This level of device typically has a strength of 1MW but some in excess of 180 times that strength are available.
Mr Tyrer said: "That is permanent retinal damage right away."
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: "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."
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.
The Metropolitan Police said inquiries to establish where the latest offence took place are under way and that there have been no arrests.