The rays definitely get in , ! If you meet a high time longhaul Captain the left side of his face will often have considerably more sun damage than the right.
Especially at this time of year the sun actually burns and is uncomfortable at altitude.
Raise the blinds , use the Telegraph or buy some of those Halfords pop out screens to stick on the window ( conventionally inside)
You won't really know how bad the damage is until it's too late.