https://www.cdc.gov/niosh/topics/aircrew/cosmicionizingradia...
Sounds like there is enough to evidence to perform a longitudinal cancer study across air transport workers to better understand the potentially increased cancer risk.
EDIT: Is hazard pay warranted? Also, perhaps airlines should have to provide estimated cumulative exposure to employees based on their flight trip logs. Estimation should be straightforward based on flight track logs combined with cosmic radiation satellite data.