A few studies by the Danes and the Kiwis, back at the turn of the century highlighted the significant increased risks of contracting Leukaemia, specifically Acute Myeloid Leukaemia (AML) for long haul pilots. I fly long haul, and I have a child recovering from AML. Do a search for the following:
Radiation-induced acute myeloid leukaemia and other cancers in commercial jet cockpit crew: a population-based cohort study.