We are exposed to low levels of radiation when we fly. You would be exposed to about 0.035 mSv (3.5 mrem) of cosmic radiation if you were to fly within the United States from the east coast to the west coast. This amount of radiation is less than the amount of radiation we receive from one chest x-ray.

For the average traveler, the amount of cosmic radiation received during flight is considered very low and safe. The Earth's atmosphere protects us from most cosmic rays, but because the air is thinner at high altitudes, passengers are exposed to higher levels than on the ground. A typical cross-country flight in the U.S. exposes you to about 0.03 millisieverts (mSv) of radiation, which is roughly equivalent to a chest X-ray. In 2026, health guidelines suggest that the annual limit for the general public is 1 mSv above natural background levels. To reach this limit, you would need to fly roughly 30 to 40 long-haul flights a year. The groups most at risk are pregnant women and frequent flyers like airline crew members, who are classified as "occupational radiation workers." Crew members on high-latitude or polar routes—where the Earth's magnetic field is weaker—receive higher doses. However, for 99% of people, the benefits of travel far outweigh the negligible risk of cosmic radiation exposure during standard commercial flights.