Not because of any security-related reason. Virgin Atlantic (the best way to fly by the way) has banned the use of Dell and Apple laptops on all of its flights and joins Korean Air and Quantas (Australia).
The reason is because these laptops pose a fire risk due to the problem with their exploding batteries.
If you are flying any of these airlines you can use your laptop in seat that provide an electrical outlet (mostly first class and some business class). The laptop batteries must fly in your checked baggage properly wrapped up.
If your seat doesn’t have a plug for your laptop you’ll just have to make due watching movies and sleeping.
Have a safe flight.