You can meaningfully reduce your radiation exposure during flights by choosing shorter routes, flying closer to the equator, and avoiding the highest cruise altitudes. At typical cruising altitude, passengers absorb roughly 3 to 8 microsieverts of radiation per hour, depending on the route. That’s a small dose for an occasional flier, but it adds up for frequent travelers, aircrew, and pregnant individuals.
Why Flights Expose You to Radiation
Earth is constantly bombarded by cosmic radiation, high-energy particles streaming in from deep space and from the sun. At ground level, the atmosphere absorbs most of it. At 35,000 to 40,000 feet, there’s far less atmosphere above you, so more of that radiation reaches your body. The particle flux actually peaks at around 50,000 to 65,000 feet, well above where commercial jets fly, but cruise altitude still exposes you to several times more radiation than you’d get on the ground.
To put the numbers in perspective: a round-trip flight from the eastern United States to Australia delivers about 71 microsieverts under normal solar conditions, while a flight to Japan delivers about 85 microsieverts because the route passes through higher latitudes. A single chest X-ray delivers roughly 20 microsieverts. So a long-haul international flight is comparable to a few chest X-rays, not nothing, but well within the range most health agencies consider safe for occasional travelers.
Choose Lower-Latitude Routes
Earth’s magnetic field acts as a shield against cosmic particles, and that shield is strongest near the equator. At the poles, the magnetic field lines funnel particles downward rather than deflecting them, so radiation penetrates deeper into the atmosphere. This means polar and high-latitude routes carry higher doses than equatorial ones.
Trans-polar flights, common on routes between North America and East Asia or Northern Europe, consistently deliver higher doses than flights of similar length closer to the equator. If you have a choice between two routings to the same destination, the one that stays at lower latitudes will reduce your exposure. For example, flying from the U.S. to Asia via a Pacific routing closer to the equator exposes you to less radiation than the shorter great-circle route that arcs near the North Pole, even though the equatorial route may take slightly longer.
Fly at Lower Altitudes When Possible
Radiation intensity increases with altitude because there is less atmospheric shielding above you. Most commercial airliners cruise between 30,000 and 45,000 feet. At the top of that range, dose rates are noticeably higher than at the bottom. You don’t typically get to choose your plane’s cruising altitude, but some practical choices follow from this fact: avoid supersonic or very high-altitude charter flights if radiation is a concern, and recognize that turboprop aircraft on shorter regional routes often cruise at 20,000 to 25,000 feet, where exposure is substantially lower.
Keep Flights Short and Infrequent
Radiation dose is cumulative. The single most effective thing you can do is simply spend fewer hours at altitude. A two-hour domestic flight delivers a fraction of the dose of a 14-hour transoceanic one. If you’re a frequent flier concerned about your annual total, consider whether some trips could be replaced with video calls or ground transportation. For context, the international guideline for public exposure (beyond natural background) is 1 millisievert per year. A handful of long-haul flights can approach or exceed that threshold, while a few short domestic trips barely register.
Airline crew members, who may log 700 to 900 hours of flight time annually, can accumulate several millisieverts per year. The occupational exposure limit is 20 millisieverts per year, and most crew stay well below that, but it’s one reason regulatory agencies classify aircrew as radiation workers in many countries.
Watch for Solar Storms
The sun goes through an 11-year activity cycle. During solar maximum, large solar flares can blast Earth with a surge of energetic particles called a solar particle event. Under normal conditions, radiation at cruise altitude runs 3 to 8 microsieverts per hour. During a major solar particle event, NOAA estimates that dose rates can spike to 200 microsieverts per hour or more for a few hours, potentially delivering 400 to 600 microsieverts over the course of a two-to-three-hour flare.
These events are rare, occurring only a few times per solar cycle, and airlines do monitor space weather advisories. Some carriers reroute flights to lower latitudes or lower altitudes during significant solar storms. If you’re planning travel during a period of high solar activity and want to be cautious, you can check NOAA’s Space Weather Prediction Center for current conditions before your flight. The practical risk to any single passenger is very low, but awareness helps if you fly frequently or are pregnant.
Use Flight Dose Calculators
The FAA provides a free tool called CARI-7 that calculates the estimated radiation dose for any specific flight route and date. You enter your departure and arrival airports, the flight date, and your cruising altitude, and it returns a dose estimate in microsieverts. It accounts for your route’s latitude, altitude, and current solar activity. This is the same tool researchers and airlines use, and it’s publicly available on the FAA’s website. If you’re a frequent flier or aircrew member tracking your annual dose, running your routes through CARI-7 gives you a concrete number to work with rather than a rough estimate.
Pregnancy and Radiation Exposure
Pregnant travelers have the most reason to be deliberate about managing flight radiation. A NIOSH study found that exposure to 0.1 milligray (about 0.36 millisieverts) or more of cosmic radiation during the first trimester may be linked to an increased risk of miscarriage. That threshold could be reached after roughly 40 to 100 hours of flight time, depending on the routes, which is well beyond what a typical passenger would accumulate but within range for aircrew working through early pregnancy.
NIOSH and NASA have also found that a pregnant flight attendant who flies through a solar particle event could receive more radiation than national and international agencies recommend for an entire pregnancy. For occasional travelers, one or two flights during pregnancy are unlikely to approach concerning levels. But if you’re pregnant and fly frequently, or if you’re planning travel during the first trimester, choosing shorter and lower-latitude routes, and fewer of them, is the most effective precaution.
Do Antioxidants Help?
Some research has explored whether antioxidant supplements can reduce the biological damage caused by ionizing radiation. A study published in the National Library of Medicine tested a combination of vitamin C, vitamin E, selenium, lipoic acid, and coenzyme Q10 in animals exposed to radiation. The combination reduced radiation lethality, and vitamin C appeared to recycle oxidized vitamin E back into its active form, making the two more effective together than either alone.
These results come from animal studies using high radiation doses far beyond what you’d encounter on a flight, so they don’t translate directly to a supplement recommendation for air travelers. No clinical trial has demonstrated that taking antioxidants before a flight meaningfully reduces the health effects of cosmic radiation at commercial altitudes. Eating a diet rich in fruits, vegetables, and other antioxidant sources is sound general health advice, but treating supplements as a radiation shield for flying isn’t supported by current evidence.
Practical Summary of What Works
- Fewer and shorter flights reduce your total hours at altitude, which is the most direct way to cut dose.
- Lower-latitude routes benefit from stronger magnetic shielding near the equator.
- Lower cruise altitudes mean more atmospheric shielding, though you rarely control this directly.
- Avoiding travel during solar storms eliminates the rare but significant dose spikes from solar particle events.
- Tracking your dose with the FAA’s CARI-7 calculator turns vague concern into concrete numbers you can manage over time.