Cosmic radiation on flights from Los Angeles (LAX) to Narita (NRT)
A flight from Los Angeles International Airport to Narita International Airport at 35,000 ft, about 11 h 6 min in the air, receives about 0.0352 mSv (35.2 µSv) of cosmic radiation: about a third of a chest X-ray. That is the FAA's CARI-7 model run for this route with the solar conditions of August 2026.
Updated · solar conditions of August 2026
- Dose
- 35.2 µSv0.0352 mSv
- Time in the air
- 11 h 6 minestimated
- Dose rate
- 3.2 µSv/haverage, 35,000 ft
- Chest X‑rays
- 0.35at 0.1 mSv each
Key facts: LAX → NRT
| Dose, standard flight | 0.0352 mSv (35.2 µSv) |
|---|---|
| Time in the air | 11 h 6 min, estimated from distance and prevailing winds |
| Cruise altitude | 35,000 ft |
| Average dose rate | 3.2 µSv/h |
| Great-circle distance | 8,755 km (5,440 mi) |
| Furthest from the equator | 47.7°N |
| Solar conditions | August 2026 |
The standard flight is CARI-7, the FAA Civil Aerospace Medical Institute's model, run on the dev machine for this route: 35,000 ft, 11 h 6 min in the air (climb 25 min, cruise 624 min, descent 17 min), effective dose per ICRP Publication 103. How it's calculated.
How the sun changes the dose on LAX → NRT
The sun's 11-year cycle moves this number. With the same 11 h 6 min at 35,000 ft, the flight would have received 0.0405 mSv in April 2020, when the sun was quiet and more galactic cosmic rays reached the atmosphere, and 0.0297 mSv in January 2026, near solar maximum: 36% more at the quiet end. In August 2026 it is 0.0352 mSv.
The numbers behind the chart
| Month | Dose | Dose |
|---|---|---|
| January 2016 | 37.5 µSv | 0.0375 mSv |
| April 2016 | 38.2 µSv | 0.0382 mSv |
| July 2016 | 38.1 µSv | 0.0381 mSv |
| October 2016 | 38.9 µSv | 0.0389 mSv |
| January 2017 | 39.1 µSv | 0.0391 mSv |
| April 2017 | 39.7 µSv | 0.0397 mSv |
| July 2017 | 39.3 µSv | 0.0393 mSv |
| October 2017 | 39.1 µSv | 0.0391 mSv |
| January 2018 | 39.5 µSv | 0.0395 mSv |
| April 2018 | 40.1 µSv | 0.0401 mSv |
| July 2018 | 40 µSv | 0.04 mSv |
| October 2018 | 40.4 µSv | 0.0404 mSv |
| January 2019 | 39.3 µSv | 0.0393 mSv |
| April 2019 | 40.4 µSv | 0.0404 mSv |
| July 2019 | 40.1 µSv | 0.0401 mSv |
| October 2019 | 40.4 µSv | 0.0404 mSv |
| January 2020 | 40.3 µSv | 0.0403 mSv |
| April 2020 | 40.5 µSv | 0.0405 mSv |
| July 2020 | 40.3 µSv | 0.0403 mSv |
| October 2020 | 40.3 µSv | 0.0403 mSv |
| January 2021 | 39.5 µSv | 0.0395 mSv |
| April 2021 | 40.4 µSv | 0.0404 mSv |
| July 2021 | 39.8 µSv | 0.0398 mSv |
| October 2021 | 39.9 µSv | 0.0399 mSv |
| January 2022 | 39.4 µSv | 0.0394 mSv |
| April 2022 | 39.2 µSv | 0.0392 mSv |
| July 2022 | 37.1 µSv | 0.0371 mSv |
| October 2022 | 37.9 µSv | 0.0379 mSv |
| January 2023 | 35.7 µSv | 0.0357 mSv |
| April 2023 | 36 µSv | 0.036 mSv |
| July 2023 | 34.6 µSv | 0.0346 mSv |
| October 2023 | 34.7 µSv | 0.0347 mSv |
| January 2024 | 33.3 µSv | 0.0333 mSv |
| April 2024 | 34 µSv | 0.034 mSv |
| July 2024 | 34.2 µSv | 0.0342 mSv |
| October 2024 | 31 µSv | 0.031 mSv |
| January 2025 | 31.8 µSv | 0.0318 mSv |
| April 2025 | 31.9 µSv | 0.0319 mSv |
| July 2025 | 31.6 µSv | 0.0316 mSv |
| October 2025 | 32.2 µSv | 0.0322 mSv |
| January 2026 | 29.8 µSv | 0.0297 mSv |
| April 2026 | 32.6 µSv | 0.0326 mSv |
| July 2026 | 34.2 µSv | 0.0342 mSv |
| August 2026 | 35.2 µSv | 0.0352 mSv |
How cruise altitude changes the dose
Flown at 31,000 ft instead, the same flight would receive 0.0261 mSv, 26% less than at 35,000 ft; at 41,000 ft it would receive 0.0496 mSv, 41% more. Same route, same time in the air, same month: only the air overhead changes.
Try it: change the altitude and the month
Every combination is its own CARI-7 run for LAX → NRT, with the same 11 h 6 min in the air. It is still a standard flight, not yours: the app calculates your exact flight.
Every combination as a table (µSv)
| Altitude | Jan 2016 | Jan 2017 | Jan 2018 | Jan 2019 | Jan 2020 | Jan 2021 | Jan 2022 | Jan 2023 | Jan 2024 | Jan 2025 | Jan 2026 | Aug 2026 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 31,000 ft | 27.7 | 28.9 | 29.1 | 29 | 29.7 | 29.1 | 29.1 | 26.4 | 24.7 | 23.6 | 22.1 | 26.1 |
| 33,000 ft | 32.5 | 33.9 | 34.2 | 34 | 34.8 | 34.2 | 34.1 | 30.9 | 28.9 | 27.6 | 25.8 | 30.5 |
| 35,000 ft | 37.5 | 39.1 | 39.5 | 39.3 | 40.3 | 39.5 | 39.4 | 35.7 | 33.3 | 31.8 | 29.8 | 35.2 |
| 37,000 ft | 42.7 | 44.6 | 45 | 44.8 | 45.9 | 45 | 44.9 | 40.6 | 37.9 | 36.2 | 33.8 | 40.1 |
| 39,000 ft | 47.9 | 50 | 50.5 | 50.3 | 51.5 | 50.5 | 50.4 | 45.5 | 42.4 | 40.5 | 37.8 | 44.9 |
| 41,000 ft | 52.9 | 55.4 | 55.9 | 55.6 | 57 | 55.9 | 55.8 | 50.3 | 46.8 | 44.6 | 41.5 | 49.6 |
The return flight: NRT → LAX
NRT → LAX receives 0.0309 mSv at 35,000 ft, 12% less than LAX → NRT, over about 9 h 46 min in the air against 11 h 6 min. The return is 1 h 20 min shorter: its track runs with the prevailing westerly winds at cruise altitude. Cosmic radiation builds up with every minute aloft, so the longer direction collects more of it along the same path.
What 35.2 µSv compares with
| Compared with | Its dose | This flight is |
|---|---|---|
| Chest X-Ray | 0.1 mSv | about a third of a chest X-ray |
| Dental X-Ray | 0.005 mSv | about 7 dental X-rays |
| Background Radiation (Daily) | 0.008 mSv | about 4.4 days of natural background radiation |
| Mammogram | 0.4 mSv | about a tenth of a mammogram |
| Head CT Scan | 2 mSv | about 2% of a head CT scan |
| Eating a Banana | 0.0001 mSv | about 352 bananas |
The comparison values are the ones the FlightDose app uses.
Why your flight will differ
- Altitude. Flown at 31,000 ft instead, the same flight would receive 0.0261 mSv, 26% less than at 35,000 ft; at 41,000 ft it would receive 0.0496 mSv, 41% more. Same route, same time in the air, same month: only the air overhead changes.
- Time in the air. Every extra 30 minutes on this route adds about 1.6 µSv. Headwinds, holding and routing change it by tens of minutes on a long flight.
- The month. The sun's 11-year cycle swings this route's dose by about 36% between quiet and active years.
- The track. Airlines fly tracks that bend with the jet stream, not the exact great circle; a track further from the equator collects more.
- Solar storms. A rare solar radiation storm can add to the dose for hours; CARI-7's monthly figures don't include one.
FlightDose calculates your exact flight.
Your date, your altitude, your time in the air, with live space weather, and a running total against the limits that matter to you.