There are many things for airline pilots to be aware of, but one unlikely thing is currently towards the top of the list: laser pointers.
On Sunday, a Virgin Atlantic flight bound for New York had to return to London's Heathrow after a pilot suffered a suspected burned retina from a laser shone at the plane shortly after takeoff.
The 252 passengers on board flight VS025 were told that one of the pilots had a "medical issue" after the plane took off from Heathrow at 8:13pm. Audio from the cockpit published online said the incident happened 6 or 7 miles west of Heathrow.
Virgin Atlantic confirmed that the plane returned as a "precautionary measure" and apologised to the passengers, who had to wait until 1pm Monday for the next available flight.
Even when they don't cause injury, lasers can obscure vision and pilots have been warning about their effects for years.
The Civil Aviation Authority (CAA) said there were 1,440 "laser incidents" affecting planes taking off from or bound for the UK in 2014, the last year for which there is complete data, compared to 746 in 2009.
The British Airline Pilots' Association said last night that it was time for lasers, which are legal and readily available in shops and online stores, to be classified as offensive weapons.
Jim McAuslan, the group's general secretary, 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."
Pointers with a range of 20 miles can be bought online for as little as £49, although retailers do warn people not to point them at aircraft.
CAA data shows that Heathrow was the most-affected UK airport in terms of laser attacks, with 48 in the first half of 2015 alone.
Police are investigating Sunday's incident and warned people that the offence of shining a laser at an aircraft carries a possible sentence of life in prison.
In October last year 28-year-old Liam Chadwick pleaded guilty and was given a six-month jail term for pointing a laser at three passenger jets and a helicopter.
Patrick Smith is a senior reporter for BuzzFeed News and is based in London.
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