I suspect the metal around the flight decks and the thick windscreens/heating elements would shield you from most of the UV. Most pilots have quality sunglasses to protect from glare, as much as from UV.
What is probably more significant, over a lifetime of flying, would be the Xrays and Gamma rays. These can penetrate low-density materials. (Such as aluminium, kevlar, and plastic.)
What to do? I'll leave that to the pilots to answer. I work just above ground level.