Cosmic radiation on flights from Narita (NRT) to Los Angeles (LAX)

Reverse: Los Angeles → Narita

A flight from Narita International Airport to Los Angeles International Airport at 35,000 ft, about 9 h 46 min in the air, receives about 0.0309 mSv (30.9 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
30.9 µSv0.0309 mSv
Time in the air
9 h 46 minestimated
Dose rate
3.2 µSv/haverage, 35,000 ft
Chest X‑rays
0.31at 0.1 mSv each

Key facts: NRT → LAX

Dose, standard flight0.0309 mSv (30.9 µSv)
Time in the air9 h 46 min, estimated from distance and prevailing winds
Cruise altitude35,000 ft
Average dose rate3.2 µSv/h
Great-circle distance8,755 km (5,440 mi)
Furthest from the equator47.7°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, 9 h 46 min in the air (climb 25 min, cruise 544 min, descent 17 min), effective dose per ICRP Publication 103. How it's calculated.

NRTLAX
Great-circle route, shaded from 2.0 µSv/h to 3.7 µSv/h. Shading is modelled from the monthly dose-rate grid; totals are CARI-7.

How the sun changes the dose on NRT → LAX

The sun's 11-year cycle moves this number. With the same 9 h 46 min at 35,000 ft, the flight would have received 0.0355 mSv in April 2020, when the sun was quiet and more galactic cosmic rays reached the atmosphere, and 0.0261 mSv in January 2026, near solar maximum: 36% more at the quiet end. In August 2026 it is 0.0309 mSv.

Dose for this flight at 35,000 ft, quarterly
0 µSv10 µSv20 µSv30 µSv40 µSv20162018202020222024202635.5 µSv26.1 µSv30.9 µSv
0 µSv10 µSv20 µSv30 µSv40 µSv20162020202435.5 µSv26.1 µSv30.9 µSv
The numbers behind the chart
MonthDoseDose
January 201632.9 µSv0.0329 mSv
April 201633.5 µSv0.0335 mSv
July 201633.4 µSv0.0334 mSv
October 201634.1 µSv0.0341 mSv
January 201734.3 µSv0.0343 mSv
April 201734.8 µSv0.0348 mSv
July 201734.4 µSv0.0344 mSv
October 201734.3 µSv0.0343 mSv
January 201834.6 µSv0.0346 mSv
April 201835.1 µSv0.0352 mSv
July 201835 µSv0.035 mSv
October 201835.5 µSv0.0355 mSv
January 201934.4 µSv0.0344 mSv
April 201935.4 µSv0.0354 mSv
July 201935.1 µSv0.0351 mSv
October 201935.4 µSv0.0354 mSv
January 202035.3 µSv0.0353 mSv
April 202035.5 µSv0.0355 mSv
July 202035.3 µSv0.0353 mSv
October 202035.3 µSv0.0353 mSv
January 202134.6 µSv0.0346 mSv
April 202135.4 µSv0.0354 mSv
July 202134.9 µSv0.0349 mSv
October 202135 µSv0.035 mSv
January 202234.6 µSv0.0346 mSv
April 202234.3 µSv0.0343 mSv
July 202232.5 µSv0.0325 mSv
October 202233.2 µSv0.0332 mSv
January 202331.3 µSv0.0313 mSv
April 202331.5 µSv0.0315 mSv
July 202330.3 µSv0.0303 mSv
October 202330.4 µSv0.0304 mSv
January 202429.2 µSv0.0292 mSv
April 202429.8 µSv0.0298 mSv
July 202430 µSv0.03 mSv
October 202427.2 µSv0.0272 mSv
January 202527.9 µSv0.0279 mSv
April 202527.9 µSv0.0279 mSv
July 202527.7 µSv0.0277 mSv
October 202528.2 µSv0.0282 mSv
January 202626.1 µSv0.0261 mSv
April 202628.6 µSv0.0286 mSv
July 202630 µSv0.03 mSv
August 202630.9 µSv0.0309 mSv

How cruise altitude changes the dose

Flown at 31,000 ft instead, the same flight would receive 0.0228 mSv, 26% less than at 35,000 ft; at 41,000 ft it would receive 0.0435 mSv, 41% 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 ft22.8 µSv
  • 33,000 ft26.8 µSv
  • 35,000 ft30.9 µSv
  • 37,000 ft35.1 µSv
  • 39,000 ft39.4 µSv
  • 41,000 ft43.5 µSv

Try it: change the altitude and the month

Every combination is its own CARI-7 run for NRT → LAX, with the same 9 h 46 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 ft24.325.325.525.42625.625.523.121.620.719.322.8
33,000 ft28.529.73029.830.53029.927.125.324.222.626.8
35,000 ft32.934.334.634.435.334.634.631.329.227.926.130.9
37,000 ft37.439.139.439.240.239.439.435.633.231.729.635.1
39,000 ft4243.944.344.145.244.344.239.937.235.533.139.4
41,000 ft46.448.64948.8504948.944.14139.136.443.5

The return flight: LAX → NRT

LAX → NRT receives 0.0352 mSv at 35,000 ft, 14% more than NRT → LAX, over about 11 h 6 min in the air against 9 h 46 min. The return takes 1 h 20 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.

Dose for each direction, standard flight
  • NRT → LAX30.9 µSv
  • LAX → NRT35.2 µSv

Cosmic radiation on Los Angeles → Narita flights

What 30.9 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 6.2 dental X-rays
Background Radiation (Daily)0.008 mSvabout 3.9 days of natural background radiation
Mammogram0.4 mSvabout 8% of a mammogram
Head CT Scan2 mSvabout 2% of a head CT scan
Eating a Banana0.0001 mSvabout 309 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 0.0228 mSv, 26% less than at 35,000 ft; at 41,000 ft it would receive 0.0435 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.

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