Flight attendants often travel across time zones, working when others normally sleep, and are exposed to cosmic radiation from the sun and space. A NIOSH study published earlier this year examined the risks of cosmic radiation, circadian disruption (from working during normal sleep hours), and other work exposures on pregnancy outcomes for flight attendants and studied 958 pregnancies among 764 female flight attendants from three U.S. airlines over 4 years. To assess each woman’s exposure to cosmic radiation and circadian disruption, company records of over 2 million flights were reviewed. This study is the first to assign two estimated radiation doses to each specific flight: one dose from ever-present galactic cosmic radiation, and one dose from a solar particle event if one occurred during that flight. Analysis of exposure to background cosmic and solar particle event radiation suggested that exposure to 0.1mGy or more may be associated with increased risk of miscarriage. Solar particle events were infrequent, but during one of the solar particle events studied, radiation dose reached 0.45 mGy on a single flight. These data suggest that if a pregnant flight attendant works on a flight that travels through a solar particle event, she could be exposed to more radiation than is recommended during pregnancy.