Cosmic radiation on flights from New York (JFK) to San Francisco (SFO)

Reverse: San Francisco → New York

A flight from John F. Kennedy International Airport to San Francisco International Airport at 35,000 ft, about 5 h 32 min in the air, receives about 0.0219 mSv (21.9 µSv) of cosmic radiation: about a fifth 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
21.9 µSv0.0219 mSv
Time in the air
5 h 32 minestimated
Dose rate
4.0 µSv/haverage, 35,000 ft
Chest X‑rays
0.22at 0.1 mSv each

Key facts: JFK → SFO

Dose, standard flight0.0219 mSv (21.9 µSv)
Time in the air5 h 32 min, estimated from distance and prevailing winds
Cruise altitude35,000 ft
Average dose rate4.0 µSv/h
Great-circle distance4,152 km (2,580 mi)
Furthest from the equator42.0°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, 5 h 32 min in the air (climb 25 min, cruise 290 min, descent 17 min), effective dose per ICRP Publication 103. How it's calculated.

JFKSFO
Great-circle route, shaded from 3.4 µSv/h to 4.2 µSv/h. Shading is modelled from the monthly dose-rate grid; totals are CARI-7.

How the sun changes the dose on JFK → SFO

The sun's 11-year cycle moves this number. With the same 5 h 32 min at 35,000 ft, the flight would have received 0.0271 mSv in April 2020, when the sun was quiet and more galactic cosmic rays reached the atmosphere, and 0.0171 mSv in January 2026, near solar maximum: 58% more at the quiet end. In August 2026 it is 0.0219 mSv.

Dose for this flight at 35,000 ft, quarterly
0 µSv10 µSv20 µSv30 µSv20162018202020222024202627.1 µSv17.1 µSv21.9 µSv
0 µSv10 µSv20 µSv30 µSv20162020202427.1 µSv17.1 µSv21.9 µSv
The numbers behind the chart
MonthDoseDose
January 201624 µSv0.024 mSv
April 201624.7 µSv0.0247 mSv
July 201624.6 µSv0.0246 mSv
October 201625.4 µSv0.0254 mSv
January 201725.7 µSv0.0257 mSv
April 201726.3 µSv0.0263 mSv
July 201725.9 µSv0.0259 mSv
October 201725.6 µSv0.0256 mSv
January 201826.1 µSv0.0261 mSv
April 201826.7 µSv0.0267 mSv
July 201826.6 µSv0.0266 mSv
October 201827.1 µSv0.0271 mSv
January 201925.9 µSv0.0259 mSv
April 201927 µSv0.027 mSv
July 201926.7 µSv0.0267 mSv
October 201927 µSv0.027 mSv
January 202026.9 µSv0.0269 mSv
April 202027.1 µSv0.0271 mSv
July 202026.9 µSv0.0269 mSv
October 202026.9 µSv0.0269 mSv
January 202126.1 µSv0.0261 mSv
April 202127 µSv0.027 mSv
July 202126.4 µSv0.0264 mSv
October 202126.5 µSv0.0265 mSv
January 202226 µSv0.026 mSv
April 202225.7 µSv0.0257 mSv
July 202223.7 µSv0.0237 mSv
October 202224.4 µSv0.0244 mSv
January 202322.3 µSv0.0223 mSv
April 202322.5 µSv0.0225 mSv
July 202321.2 µSv0.0212 mSv
October 202321.4 µSv0.0214 mSv
January 202420.1 µSv0.0201 mSv
April 202420.7 µSv0.0207 mSv
July 202420.9 µSv0.0209 mSv
October 202418.2 µSv0.0182 mSv
January 202518.8 µSv0.0188 mSv
April 202518.9 µSv0.0189 mSv
July 202518.7 µSv0.0187 mSv
October 202519.2 µSv0.0192 mSv
January 202617.1 µSv0.0171 mSv
April 202619.5 µSv0.0195 mSv
July 202620.9 µSv0.0209 mSv
August 202621.9 µSv0.0219 mSv

How cruise altitude changes the dose

Flown at 31,000 ft instead, the same flight would receive 0.0159 mSv, 27% less than at 35,000 ft; at 41,000 ft it would receive 0.0317 mSv, 45% 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 ft15.9 µSv
  • 33,000 ft18.8 µSv
  • 35,000 ft21.9 µSv
  • 37,000 ft25.1 µSv
  • 39,000 ft28.4 µSv
  • 41,000 ft31.7 µSv

Try it: change the altitude and the month

Every combination is its own CARI-7 run for JFK → SFO, with the same 5 h 32 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 ft17.418.618.818.719.418.818.816.214.713.812.515.9
33,000 ft20.62222.322.12322.322.319.117.316.214.818.8
35,000 ft2425.726.125.926.926.12622.320.118.817.121.9
37,000 ft27.629.63029.730.93029.925.623.121.619.625.1
39,000 ft31.333.63433.835.234.13428.926.124.322.128.4
41,000 ft3537.638.237.839.538.238.132.32927.124.531.7

The return flight: SFO → JFK

SFO → JFK receives 0.0185 mSv at 35,000 ft, 15% less than JFK → SFO, over about 4 h 45 min in the air against 5 h 32 min. The return is 47 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
  • JFK → SFO21.9 µSv
  • SFO → JFK18.5 µSv

Cosmic radiation on San Francisco → New York flights

What 21.9 µSv compares with

Compared withIts doseThis flight is
Chest X-Ray0.1 mSvabout a fifth of a chest X-ray
Dental X-Ray0.005 mSvabout 4.4 dental X-rays
Background Radiation (Daily)0.008 mSvabout 2.7 days of natural background radiation
Mammogram0.4 mSvabout 5% of a mammogram
Head CT Scan2 mSvabout 1% of a head CT scan
Eating a Banana0.0001 mSvabout 219 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 0.0159 mSv, 27% less than at 35,000 ft; at 41,000 ft it would receive 0.0317 mSv, 45% 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 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 58% 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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