The British Airline Pilots Association has called for more action in tackling the growing use of lasers.
The co-pilot reported feeling sick after the incident and it was decided it was safer to cut short the transatlantic crossing and return to Heathrow.
According to Virgin Atlantic spokesman, Jaime Fraser said "the decision was a "precautionary measure". "We are working with the authorities to identify the source of the laser."
The flight was grounded overnight, and the 252 passengers put up in hotels.
No arrest has been made yet.
It believes lasers should classified as an offensive weapon.