Cosmic radiation on flights from London (LHR) to Chicago (ORD)

Reverse: Chicago → London

A flight from London Heathrow Airport to Chicago O'Hare International Airport at 35,000 ft, about 8 h 14 min in the air, receives about 0.0362 mSv (36.2 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
36.2 µSv0.0362 mSv
Time in the air
8 h 14 minestimated
Dose rate
4.4 µSv/haverage, 35,000 ft
Chest X‑rays
0.36at 0.1 mSv each

Key facts: LHR → ORD

Dose, standard flight0.0362 mSv (36.2 µSv)
Time in the air8 h 14 min, estimated from distance and prevailing winds
Cruise altitude35,000 ft
Average dose rate4.4 µSv/h
Great-circle distance6,344 km (3,942 mi)
Furthest from the equator56.6°N
Solar conditionsAugust 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, 8 h 14 min in the air (climb 25 min, cruise 452 min, descent 17 min), effective dose per ICRP Publication 103. How it's calculated.

LHRORD
Great-circle route, shaded from 4.0 µSv/h to 4.5 µSv/h. Shading is modelled from the monthly dose-rate grid; totals are CARI-7.

How the sun changes the dose on LHR → ORD

The sun's 11-year cycle moves this number. With the same 8 h 14 min at 35,000 ft, the flight would have received 0.0469 mSv in April 2020, when the sun was quiet and more galactic cosmic rays reached the atmosphere, and 0.0275 mSv in January 2026, near solar maximum: 71% more at the quiet end. In August 2026 it is 0.0362 mSv.

Dose for this flight at 35,000 ft, quarterly
0 µSv20 µSv40 µSv60 µSv20162018202020222024202646.9 µSv27.5 µSv36.2 µSv
0 µSv20 µSv40 µSv60 µSv20162020202446.9 µSv27.5 µSv36.2 µSv
The numbers behind the chart
MonthDoseDose
January 201640.4 µSv0.0404 mSv
April 201641.8 µSv0.0418 mSv
July 201641.6 µSv0.0416 mSv
October 201643.3 µSv0.0433 mSv
January 201743.9 µSv0.0439 mSv
April 201745.2 µSv0.0452 mSv
July 201744.2 µSv0.0442 mSv
October 201743.7 µSv0.0437 mSv
January 201844.6 µSv0.0446 mSv
April 201846 µSv0.046 mSv
July 201845.8 µSv0.0457 mSv
October 201846.8 µSv0.0468 mSv
January 201944.2 µSv0.0442 mSv
April 201946.7 µSv0.0467 mSv
July 201945.9 µSv0.0459 mSv
October 201946.7 µSv0.0467 mSv
January 202046.4 µSv0.0464 mSv
April 202046.9 µSv0.0469 mSv
July 202046.5 µSv0.0465 mSv
October 202046.5 µSv0.0465 mSv
January 202144.7 µSv0.0447 mSv
April 202146.7 µSv0.0467 mSv
July 202145.4 µSv0.0454 mSv
October 202145.6 µSv0.0456 mSv
January 202244.5 µSv0.0445 mSv
April 202243.9 µSv0.0439 mSv
July 202239.7 µSv0.0397 mSv
October 202241.1 µSv0.0411 mSv
January 202337 µSv0.037 mSv
April 202337.5 µSv0.0375 mSv
July 202335 µSv0.035 mSv
October 202335.2 µSv0.0352 mSv
January 202432.9 µSv0.0329 mSv
April 202434 µSv0.034 mSv
July 202434.3 µSv0.0343 mSv
October 202429.4 µSv0.0294 mSv
January 202530.6 µSv0.0306 mSv
April 202530.6 µSv0.0306 mSv
July 202530.2 µSv0.0302 mSv
October 202531.1 µSv0.0311 mSv
January 202627.5 µSv0.0275 mSv
April 202631.7 µSv0.0317 mSv
July 202634.3 µSv0.0343 mSv
August 202636.2 µSv0.0362 mSv

How cruise altitude changes the dose

Flown at 31,000 ft instead, the same flight would receive 0.0261 mSv, 28% less than at 35,000 ft; at 41,000 ft it would receive 0.0531 mSv, 47% more. Same route, same time in the air, same month: only the air overhead changes.

Dose for this flight by cruise altitude, August 2026
  • 31,000 ft26.1 µSv
  • 33,000 ft30.9 µSv
  • 35,000 ft36.2 µSv
  • 37,000 ft41.6 µSv
  • 39,000 ft47.3 µSv
  • 41,000 ft53.1 µSv

Try it: change the altitude and the month

Every combination is its own CARI-7 run for LHR → ORD, with the same 8 h 14 min in the air. It is still a standard flight, not yours: the app calculates your exact flight.

Every combination as a table (µSv)
AltitudeJan 2016Jan 2017Jan 2018Jan 2019Jan 2020Jan 2021Jan 2022Jan 2023Jan 2024Jan 2025Jan 2026Aug 2026
31,000 ft2931.431.931.633.131.931.826.623.822.22026.1
33,000 ft34.537.43837.639.53837.931.628.226.223.730.9
35,000 ft40.443.944.644.246.444.744.53732.930.627.536.2
37,000 ft46.750.751.651.153.751.651.442.637.835.131.541.6
39,000 ft53.157.958.958.361.45958.748.442.839.735.547.3
41,000 ft59.865.366.565.869.466.666.354.44844.339.653.1

The return flight: ORD → LHR

ORD → LHR receives 0.0312 mSv at 35,000 ft, 14% less than LHR → ORD, over about 7 h 11 min in the air against 8 h 14 min. The return is 1 h 3 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.

Dose for each direction, standard flight
  • LHR → ORD36.2 µSv
  • ORD → LHR31.2 µSv

Cosmic radiation on Chicago → London flights

What 36.2 µSv compares with

Compared withIts doseThis flight is
Chest X-Ray0.1 mSvabout a third of a chest X-ray
Dental X-Ray0.005 mSvabout 7.2 dental X-rays
Background Radiation (Daily)0.008 mSvabout 4.5 days of natural background radiation
Mammogram0.4 mSvabout a tenth of a mammogram
Head CT Scan2 mSvabout 2% of a head CT scan
Eating a Banana0.0001 mSvabout 362 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, 28% less than at 35,000 ft; at 41,000 ft it would receive 0.0531 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 71% 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.

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