The dose equivalent to air carrier crewmembers from galactic cosmic radiation was estimated for each of 32 nonstop flights on a variety of routes to and from, or within, the contiguous United States. Flying times were from 0.4 to 13 hours. The annual dose equivalents received on the flights ranged from 0.2 to 9.1 mSv (20 to 910 mrem), or 0.4 to 18% of the recommended annual limit for occupational exposure of an adult. We reviewed some of the characteristics of galactic and solar cosmic radiation and provided example calculations for estimating radiation-induced risks of fatal cancer, genetic defects and harm to an embryo or fetus. The estimated increased risk of dying from cancer because of galactic radiation exposure received during 20 years of flying ranged from 0.1 to 5 in 1,000. For the adult U.S. population the risk of dying from cancer is about 220 in 1,000.