Cosmic radiation on flights from Chicago (ORD) to London (LHR)
A flight from Chicago O'Hare International Airport to London Heathrow Airport at 35,000 ft, about 7 h 11 min in the air, receives about 0.0312 mSv (31.2 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
- 31.2 µSv0.0312 mSv
- Time in the air
- 7 h 11 minestimated
- Dose rate
- 4.3 µSv/haverage, 35,000 ft
- Chest X‑rays
- 0.31at 0.1 mSv each
Key facts: ORD → LHR
| Dose, standard flight | 0.0312 mSv (31.2 µSv) |
|---|---|
| Time in the air | 7 h 11 min, estimated from distance and prevailing winds |
| Cruise altitude | 35,000 ft |
| Average dose rate | 4.3 µSv/h |
| Great-circle distance | 6,344 km (3,942 mi) |
| Furthest from the equator | 56.6°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, 7 h 11 min in the air (climb 25 min, cruise 389 min, descent 17 min), effective dose per ICRP Publication 103. How it's calculated.
How the sun changes the dose on ORD → LHR
The sun's 11-year cycle moves this number. With the same 7 h 11 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 0.0238 mSv in January 2026, near solar maximum: 70% more at the quiet end. In August 2026 it is 0.0312 mSv.
The numbers behind the chart
| Month | Dose | Dose |
|---|---|---|
| January 2016 | 34.9 µSv | 0.0349 mSv |
| April 2016 | 36.1 µSv | 0.0361 mSv |
| July 2016 | 35.9 µSv | 0.0359 mSv |
| October 2016 | 37.4 µSv | 0.0374 mSv |
| January 2017 | 37.9 µSv | 0.0379 mSv |
| April 2017 | 39 µSv | 0.039 mSv |
| July 2017 | 38.2 µSv | 0.0382 mSv |
| October 2017 | 37.7 µSv | 0.0377 mSv |
| January 2018 | 38.5 µSv | 0.0385 mSv |
| April 2018 | 39.7 µSv | 0.0397 mSv |
| July 2018 | 39.5 µSv | 0.0395 mSv |
| October 2018 | 40.4 µSv | 0.0404 mSv |
| January 2019 | 38.2 µSv | 0.0382 mSv |
| April 2019 | 40.3 µSv | 0.0403 mSv |
| July 2019 | 39.7 µSv | 0.0397 mSv |
| October 2019 | 40.3 µSv | 0.0403 mSv |
| January 2020 | 40.1 µSv | 0.0401 mSv |
| April 2020 | 40.5 µSv | 0.0405 mSv |
| July 2020 | 40.1 µSv | 0.0401 mSv |
| October 2020 | 40.1 µSv | 0.0401 mSv |
| January 2021 | 38.6 µSv | 0.0386 mSv |
| April 2021 | 40.3 µSv | 0.0403 mSv |
| July 2021 | 39.2 µSv | 0.0392 mSv |
| October 2021 | 39.4 µSv | 0.0394 mSv |
| January 2022 | 38.4 µSv | 0.0384 mSv |
| April 2022 | 37.9 µSv | 0.0379 mSv |
| July 2022 | 34.3 µSv | 0.0343 mSv |
| October 2022 | 35.5 µSv | 0.0355 mSv |
| January 2023 | 31.9 µSv | 0.0319 mSv |
| April 2023 | 32.4 µSv | 0.0324 mSv |
| July 2023 | 30.2 µSv | 0.0302 mSv |
| October 2023 | 30.4 µSv | 0.0304 mSv |
| January 2024 | 28.4 µSv | 0.0284 mSv |
| April 2024 | 29.4 µSv | 0.0294 mSv |
| July 2024 | 29.6 µSv | 0.0296 mSv |
| October 2024 | 25.4 µSv | 0.0254 mSv |
| January 2025 | 26.4 µSv | 0.0264 mSv |
| April 2025 | 26.4 µSv | 0.0264 mSv |
| July 2025 | 26.1 µSv | 0.0261 mSv |
| October 2025 | 26.9 µSv | 0.0269 mSv |
| January 2026 | 23.8 µSv | 0.0238 mSv |
| April 2026 | 27.4 µSv | 0.0274 mSv |
| July 2026 | 29.6 µSv | 0.0296 mSv |
| August 2026 | 31.2 µSv | 0.0312 mSv |
How cruise altitude changes the dose
Flown at 31,000 ft instead, the same flight would receive 0.0225 mSv, 28% less than at 35,000 ft; at 41,000 ft it would receive 0.0458 mSv, 47% 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 ORD → LHR, with the same 7 h 11 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 | 25 | 27.1 | 27.5 | 27.3 | 28.6 | 27.5 | 27.4 | 23 | 20.6 | 19.1 | 17.3 | 22.5 |
| 33,000 ft | 29.8 | 32.3 | 32.8 | 32.5 | 34.1 | 32.8 | 32.7 | 27.3 | 24.4 | 22.6 | 20.4 | 26.7 |
| 35,000 ft | 34.9 | 37.9 | 38.5 | 38.2 | 40.1 | 38.6 | 38.4 | 31.9 | 28.4 | 26.4 | 23.8 | 31.2 |
| 37,000 ft | 40.3 | 43.8 | 44.5 | 44.1 | 46.4 | 44.6 | 44.4 | 36.8 | 32.6 | 30.3 | 27.2 | 36 |
| 39,000 ft | 45.9 | 50 | 50.9 | 50.3 | 53 | 50.9 | 50.7 | 41.8 | 37 | 34.3 | 30.7 | 40.8 |
| 41,000 ft | 51.7 | 56.4 | 57.4 | 56.8 | 59.9 | 57.5 | 57.2 | 46.9 | 41.4 | 38.3 | 34.2 | 45.8 |
The return flight: LHR → ORD
LHR → ORD receives 0.0362 mSv at 35,000 ft, 16% more than ORD → LHR, over about 8 h 14 min in the air against 7 h 11 min. The return takes 1 h 3 min longer: its track runs against 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 31.2 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 6.2 dental X-rays |
| Background Radiation (Daily) | 0.008 mSv | about 3.9 days of natural background radiation |
| Mammogram | 0.4 mSv | about 8% of a mammogram |
| Head CT Scan | 2 mSv | about 2% of a head CT scan |
| Eating a Banana | 0.0001 mSv | about 312 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 0.0225 mSv, 28% less than at 35,000 ft; at 41,000 ft it would receive 0.0458 mSv, 47% 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 2.2 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 70% 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.