Frequent-flyer dose math: when it actually starts to matter

This guide does the arithmetic that everyone wants to do in their head when they look at a flight log. Given a baseline cosmic-radiation dose rate at cruise altitude, how does annual dose stack up against the reference limits? The answer scales almost linearly with flight hours, with two important second-order effects (cruise altitude and latitude) that we cover briefly and which our polar guide and altitude guide handle in depth.

The baseline dose rate

A reasonable working number for in-flight effective dose rate, averaged over the route mix of a US-based business traveller, is 5 µSv per flight hour. This is an approximate mean from CARI-7A outputs over a representative basket of routes at the 2026 solar-cycle phase ^[1]. The range is roughly:

Route type	Typical in-flight dose rate (µSv/hr)
Short-haul domestic US, FL320–FL360	3.5–4.5
Transcontinental US, FL370–FL400	4.5–5.5
Transatlantic NATS, FL370	5.0–6.0
Transpolar (NYC–HKG, NRT–YYZ), FL390–FL410	6.0–7.0
Equatorial long-haul (SIN–SYD, GRU–JNB)	3.0–4.0

For the rest of this guide we use 5 µSv/hr as the working assumption for a US-based traveller. Adjust upward 20–40% if your pattern is polar-heavy.

The annual dose ladder

Annual flight hours, multiplied by 5 µSv/hr, gives annual flight dose. Compared against reference values:

Annual flight hours	Equivalent flying volume	Annual flight dose (mSv)	Where this sits
10	~ 2 short-haul round trips	0.05	Rounding error on background
25	~ 1 transatlantic + a few domestic	0.13	10% of US background; well under ICRP public 1 mSv
50	Light business travel — fortnightly domestic + 1 international/yr	0.25	~ Half the cosmic component of US background
100	Active business travel — bi-monthly transatlantic + weekly domestic	0.50	Half the ICRP public 1 mSv
200	Heavy business travel — monthly transatlantic + weekly domestic, all year	1.0	Crosses ICRP-103 public 1 mSv
400	Very heavy — biweekly transatlantic, near-constant US domestic	2.0	2x ICRP public; ~ 33% of FAA aircrew action 6 mSv
600	Lower bound of short-haul cabin-crew hours	3.0	50% of FAA aircrew action level
800	Typical long-haul aircrew	4.0	67% of FAA aircrew action level
1,200	Hard ceiling on FAA Part 121 line aircrew (14 CFR 121.471 caps duty/flight time, not flight time alone, but ~1,000 hr/yr is a practical maximum)	6.0	Hits FAA aircrew action level 6 mSv

(For 14 CFR 121.471 — flight-time limitations on US Part 121 carriers — see the eCFR reference ^[2].)

What each reference number actually means

• US background — 6.2 mSv/yr. NCRP Report 160 (2009) puts total US per-capita exposure at about 6.2 mSv/yr, of which roughly 50% is medical, 35% is radon, and the remainder is cosmic, terrestrial, and internal ^[3].
• Cosmic component of US background — 0.33 mSv/yr. The ground-level cosmic-radiation contribution at the US per-capita altitude.
• ICRP public limit — 1 mSv/yr. Reference for additional dose from controllable sources; cosmic is technically excluded, but the figure is the most familiar benchmark. ICRP-103 ^[4].
• FAA aircrew action level — 6 mSv/yr. NCRP 132 / FAA AC 120-61B. Triggers carrier review of crew schedule. Not an enforced cap ^[5].
• ICRP occupational limit — 20 mSv/yr (averaged over 5 years). Enforced for radiation workers under EU EURATOM rules; recommended elsewhere ^[4].

Polar-heavy fliers need to multiply by ~1.3

If your pattern is dominated by polar transatlantic or transpolar routes — for example, frequent JFK-LHR + JFK-NRT — bump the 5 µSv/hr baseline up to about 6.5 µSv/hr and re-do the arithmetic. Annual dose figures shift correspondingly. A reader doing 200 hours of polar-heavy long-haul a year is at roughly 1.3 mSv/yr, comfortably above the ICRP public 1 mSv reference.

What this does not tell you

• It does not tell you individual cancer risk. The translation of mSv to lifetime attributable risk depends on BEIR VII coefficients ^[6] applied to a population, not to an individual.
• It does not include solar-particle-event variation (see our SPE guide).
• It does not adjust for individual radiosensitivity factors (age at first exposure, sex, prior medical radiation history).

The right way to think about it

Most non-occupational fliers are well below the ICRP public 1 mSv reference and roughly comparable to the cosmic component of natural background. Heavy business travel crosses the public reference but stays well below the FAA aircrew action level. Only the heaviest long-haul aircrew patterns approach the FAA 6 mSv/yr figure, and even those remain well below the ICRP-103 20 mSv/yr occupational limit.

The two practical levers if you want to reduce annual dose: reduce hours (obviously) and reduce polar exposure where route choice exists. Aircraft type and seat selection do not meaningfully change the answer.

For your specific log, run the numbers — either via the free FAA CARI-7A web tool segment by segment, or as a bundle via our PDF report.

How the polar attribution metric changes the picture

The headline number on a FlightRadiation report is annual dose, but the more actionable number is often the polar attribution — what fraction of that annual dose came from segments above 60° geomagnetic latitude. For most US-based business fliers, polar segments are a small minority of trips but a large share of dose. Reducing polar exposure is the single highest-leverage adjustment available to a frequent flier, particularly for transatlantic routes where mid-latitude routings exist (e.g. NATS tracks that stay south of 55° N during favourable jet-stream patterns).

Flying pattern	Annual hours	Annual mSv	Polar share
US domestic only (transcontinental)	120	0.55	0%
US domestic + monthly mid-latitude transatlantic	200	1.0	15%
US domestic + monthly polar transatlantic	220	1.3	25%
Heavy long-haul: weekly mixed transcon + biweekly transpolar Asia	450	2.8	40%
Long-haul polar specialist	600	4.1	55%

The career-cumulative picture

For long-term planning, the annual figure matters less than the career cumulative. Over a 30-year career holding a pattern constant:

• Light business travel (50 hr/yr) — about 7.5 mSv lifetime additional cosmic dose from flying.
• Heavy business travel (200 hr/yr) — about 30 mSv lifetime.
• Long-haul aircrew (800 hr/yr) — about 120 mSv lifetime.
• Polar long-haul aircrew (800 hr/yr polar-heavy) — about 180 mSv lifetime.

The 180 mSv lifetime figure is high enough that the BEIR VII risk coefficients give a non-trivial lifetime attributable risk increment — on the order of a 1% absolute increase in lifetime cancer risk over the background lifetime cancer mortality of roughly 23% for a typical adult ^[6]. This is the regime in which empirical evidence from the NIOSH flight-attendant cohort actually starts to detect cancer-incidence elevations (see our flight attendants and cancer guide).

Two common mistakes in mental arithmetic

• Confusing flight hours with travel hours. Block time (gate to gate) is roughly 30–60 minutes longer than airborne time on most flights, and only airborne time accumulates cosmic dose at the cruise rate. We use airborne time in the math above.
• Forgetting climb / descent. Climb and descent contribute meaningful dose for short-haul flying but are a small share of long-haul. CARI-7A integrates the climb and descent profile automatically; if you are doing back-of-envelope math, treat the dose rate during climb/descent as roughly half the cruise rate, averaged.

The arithmetic of a 30-year career projection

The FlightRadiation report includes a career-cumulative projection because it changes the framing. An annual dose of 1 mSv sounds small in any given year; 30 mSv accumulated across a working career is the figure that BEIR VII risk coefficients are designed to be applied to. The relevant arithmetic, holding a flying pattern constant:

• Light flier (50 hr/yr): 7.5 mSv over 30 years.
• Active business flier (150 hr/yr): 22.5 mSv over 30 years.
• Heavy business flier (300 hr/yr): 45 mSv over 30 years.
• Long-haul cabin crew (800 hr/yr): 120 mSv over 30 years.
• Polar long-haul crew (800 hr/yr polar-heavy): 180 mSv over 30 years.

These numbers are linear projections that ignore solar-cycle variation across decades (which would cancel out roughly) and ignore changes in flying intensity across a career (which usually go down with time, not up). They are useful as order-of-magnitude figures, not as precision forecasts.

How dose compares to natural background year-on-year

One useful frame: how many years of your flying equals one year of US per-capita background? With US per-capita background at 6.2 mSv/yr (NCRP 160), and using a 5 µSv/hr in-flight rate:

• For a flier doing 50 hr/yr, one year of flying equals about 14 days of US background.
• For a flier doing 200 hr/yr, one year of flying equals about 60 days of US background — one sixth of a year.
• For a long-haul aircrew member doing 800 hr/yr, one year of flying equals about 240 days of US background — most of a year, but still less than one annual background dose.
• For a polar specialist at 800 hr/yr, one year of flying can match or slightly exceed one annual US background dose.

None of these patterns delivers dose that is large in absolute terms. The case for paying attention to flight dose is not that the numbers are alarming; it is that they are non-trivial for the heaviest patterns and that flight dose is one of the few dose sources adults can actively modulate in their own behaviour.

Why "average" matters less than "consistency"

Two fliers with identical 200 hr/yr averages can have very different dose profiles. Flier A does a steady 4 transatlantic round-trips per month. Flier B does no flying for nine months and then a five-week intensive trip block. Their annual doses are equal in expectation, but flier B's dose is concentrated. From a stochastic-risk perspective both are equivalent under the LNT model; from a practical health-decision perspective, neither pattern triggers a meaningful difference. The numbers are simply useful for understanding what your total exposure is and how it compares.

Last reviewed 30 June 2026 · See our methodology and sources.