I read a research report regarding flight crew exposure to cosmic radiation. The resarchers found unusal high precentage of skin cancer etc. However when the research was done with military pilots (fighter pilots) no abnormal effects were found. A fighter pilot is far more exposed to cosmic radiation (canopy) and the researchers pointed out that the aircraft fuselage should give sufficient blockage fram radiation.
As a followup, they compared the flight crews flying to sunny destinations and those flying destinations such as britain-iceland. There was a big difference. The researchers suggested that the pilot where in fact well shelterd while in the aircraft. The effects where instead due to the large number of short "burns" that i.e. charter crews where exposed to.
I found the research quite interesting