It pays to be sunsmart at 30,000 feet as well as at the beach.
A US dermatologist says is it entirely possible to be burned while on a plane and we should pack sunblock in carry-on bags as a precaution.
Marc Glashofer told Conde Nast Traveler that while aircraft windows block UVB rays, which cause sunburn, UVA rays can penetrate the glass. These rays hit the skin at a deeper level and can potentially cause skin cancer.
It's a problem that's of a particular concern to pilots. In a recent study, JAMA Dermatology found that one hour at 30,000 feet exposed pilots to the same amount of UV radiation from 20-minute tanning bed session.
As the windows in plane cabins are smaller, passengers are less exposed - but it can add up.
Another dermatologist, Joel Cohen, said he pulled down the window shades when it was sunny - however clouds and snow can also reflect UV rays and cause skin damage.
Both recommended wearing a broad-spectrum SPF 30 sunscreen lotion, which should be applied every two hours.