Cosmic radiation on flights from Sydney (SYD) to Los Angeles (LAX)

Reverse: Los Angeles → Sydney

A flight from Sydney Kingsford Smith International Airport to Los Angeles International Airport at 35,000 ft, about 14 h 12 min in the air, receives about 0.0285 mSv (28.5 µSv) of cosmic radiation: about 28% 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
28.5 µSv0.0285 mSv
Time in the air
14 h 12 minestimated
Dose rate
2.0 µSv/haverage, 35,000 ft
Chest X‑rays
0.28at 0.1 mSv each

Key facts: SYD → LAX

Dose, standard flight0.0285 mSv (28.5 µSv)
Time in the air14 h 12 min, estimated from distance and prevailing winds
Cruise altitude35,000 ft
Average dose rate2.0 µSv/h
Great-circle distance12,061 km (7,494 mi)
Furthest from the equator33.9°S
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, 14 h 12 min in the air (climb 25 min, cruise 810 min, descent 17 min), effective dose per ICRP Publication 103. How it's calculated.

SYDLAX
Great-circle route, shaded from 1.5 µSv/h to 3.3 µSv/h. Shading is modelled from the monthly dose-rate grid; totals are CARI-7.

How the sun changes the dose on SYD → LAX

The sun's 11-year cycle moves this number. With the same 14 h 12 min at 35,000 ft, the flight would have received 0.0306 mSv in April 2020, when the sun was quiet and more galactic cosmic rays reached the atmosphere, and 0.026 mSv in January 2026, near solar maximum: 18% more at the quiet end. In August 2026 it is 0.0285 mSv.

Dose for this flight at 35,000 ft, quarterly
0 µSv10 µSv20 µSv30 µSv40 µSv20162018202020222024202630.6 µSv25.9 µSv28.5 µSv
0 µSv10 µSv20 µSv30 µSv40 µSv20162020202430.6 µSv25.9 µSv28.5 µSv
The numbers behind the chart
MonthDoseDose
January 201629.4 µSv0.0294 mSv
April 201629.7 µSv0.0297 mSv
July 201629.6 µSv0.0296 mSv
October 201629.9 µSv0.03 mSv
January 201730.1 µSv0.0301 mSv
April 201730.3 µSv0.0303 mSv
July 201730.1 µSv0.0301 mSv
October 201730 µSv0.03 mSv
January 201830.2 µSv0.0302 mSv
April 201830.4 µSv0.0304 mSv
July 201830.4 µSv0.0304 mSv
October 201830.6 µSv0.0306 mSv
January 201930.1 µSv0.0301 mSv
April 201930.6 µSv0.0306 mSv
July 201930.4 µSv0.0304 mSv
October 201930.6 µSv0.0306 mSv
January 202030.5 µSv0.0305 mSv
April 202030.6 µSv0.0306 mSv
July 202030.5 µSv0.0305 mSv
October 202030.5 µSv0.0305 mSv
January 202130.2 µSv0.0302 mSv
April 202130.6 µSv0.0306 mSv
July 202130.3 µSv0.0303 mSv
October 202130.4 µSv0.0304 mSv
January 202230.2 µSv0.0302 mSv
April 202230.1 µSv0.0301 mSv
July 202229.3 µSv0.0293 mSv
October 202229.6 µSv0.0295 mSv
January 202328.6 µSv0.0286 mSv
April 202328.8 µSv0.0288 mSv
July 202328.2 µSv0.0282 mSv
October 202328.2 µSv0.0282 mSv
January 202427.6 µSv0.0276 mSv
April 202427.9 µSv0.0279 mSv
July 202428 µSv0.028 mSv
October 202426.6 µSv0.0266 mSv
January 202526.9 µSv0.0269 mSv
April 202527 µSv0.027 mSv
July 202526.8 µSv0.0268 mSv
October 202527.1 µSv0.0271 mSv
January 202625.9 µSv0.026 mSv
April 202627.3 µSv0.0273 mSv
July 202628 µSv0.028 mSv
August 202628.5 µSv0.0285 mSv

How cruise altitude changes the dose

Flown at 31,000 ft instead, the same flight would receive 0.0214 mSv, 25% less than at 35,000 ft; at 41,000 ft it would receive 0.0386 mSv, 36% 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 ft21.4 µSv
  • 33,000 ft24.9 µSv
  • 35,000 ft28.5 µSv
  • 37,000 ft32 µSv
  • 39,000 ft35.5 µSv
  • 41,000 ft38.6 µSv

Try it: change the altitude and the month

Every combination is its own CARI-7 run for SYD → LAX, with the same 14 h 12 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 ft22.122.622.722.622.922.722.621.520.720.219.521.4
33,000 ft25.726.326.426.326.626.426.42524.123.622.724.9
35,000 ft29.430.130.230.130.530.230.228.627.626.925.928.5
37,000 ft33.133.93433.934.4343432.331.130.329.232
39,000 ft36.737.537.737.638.137.737.735.734.433.632.335.5
41,000 ft4040.941.14141.541.141.138.937.536.535.138.6

The return flight: LAX → SYD

LAX → SYD receives 0.0285 mSv at 35,000 ft, about the same as SYD → LAX, over about 14 h 12 min in the air against 14 h 12 min. The two directions take about the same time: the route runs mostly north–south, across the prevailing westerly winds rather than into them.

Dose for each direction, standard flight
  • SYD → LAX28.5 µSv
  • LAX → SYD28.5 µSv

Cosmic radiation on Los Angeles → Sydney flights

What 28.5 µSv compares with

Compared withIts doseThis flight is
Chest X-Ray0.1 mSvabout 28% of a chest X-ray
Dental X-Ray0.005 mSvabout 5.7 dental X-rays
Background Radiation (Daily)0.008 mSvabout 3.6 days of natural background radiation
Mammogram0.4 mSvabout 7% of a mammogram
Head CT Scan2 mSvabout 1% of a head CT scan
Eating a Banana0.0001 mSvabout 285 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 0.0214 mSv, 25% less than at 35,000 ft; at 41,000 ft it would receive 0.0386 mSv, 36% 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 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 18% 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.

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