Frequently asked

Definitive answers to the questions readers ask most about in-flight cosmic radiation, the CARI-7 dose model, and our PDF report.

• How accurate is the dose number on a FlightRadiation report?

  The CARI-7 / CARI-7A model used by the FAA has been validated against in-flight neutron and ionizing-radiation measurements for several decades (see Friedberg & Copeland). The model's stated uncertainty for galactic-cosmic-ray-driven effective dose at typical cruise altitudes is on the order of ±25% at the 2σ level. We carry that uncertainty band through to the report; a value of "5.4 mSv/yr" should be read as roughly "4 to 7 mSv/yr".

• What does the PDF actually contain?

  A single-flight report with: the flight's effective dose in microsieverts, everyday comparisons (chest X-ray, a year of natural background), a bar chart against the ICRP-103 public limit (1 mSv/yr), pregnancy reference (1 mSv), FAA aircrew action level (6 mSv/yr), and occupational limit (20 mSv/yr averaged over 5 years), plus an annualized figure if you told us how often you fly the route.

  If the passenger profile is "pregnant" we also include the ICRP-103 §5.4.2 gestational fetus limit (1 mSv across the remainder of declared pregnancy) and a pointer to discuss the pattern with an obstetrician.

• How is this different from the free FAA CARI-7A web tool?

  The CARI-7A web tool computes a flight's dose and returns a bare number with no context. FlightRadiation takes the same single-flight calculation and makes it readable: everyday comparisons like a chest X-ray, the ICRP-103 reference levels, a pregnancy note where relevant, and an annualized figure if you fly the route often, all in a printable PDF. The underlying physics is identical; we are not a different model, we are different framing.

• Is flying during pregnancy dangerous?

  For occasional flying, no. ACOG Committee Opinion 656 notes that cumulative fetal exposure below 50 mGy has not been associated with an increase in fetal anomalies or pregnancy loss. For comparison, a single transatlantic round trip is on the order of 0.1 mSv to the fetus.

  The relevant occupational reference, ICRP-103 §5.4.2, is 1 mSv to the conceptus across the remainder of pregnancy once it is declared, roughly 30 to 50 hours of transatlantic flying. Frequent flying during pregnancy is worth a discussion with an obstetrician, and for crew with the employer's radiation-safety officer. See our detailed guide: Pregnancy and flying.

• Should I avoid polar routes?

  For most fliers, no. A typical leisure flier doing one or two transatlantic trips a year is exposed well below the ICRP-103 public 1 mSv reference even if both crossings are polar.

  For frequent fliers, polar routings carry the most reducible dose, because geomagnetic shielding falls off steeply north of 60° latitude. Where you have a choice of routing, a more southerly, mid-latitude flight reduces the dose meaningfully. See Polar routes and cosmic dose.

• What is a solar particle event and should I worry about it?

  A solar particle event (SPE) is a burst of high-energy protons accelerated by a solar flare or coronal mass ejection. Large SPEs (NOAA S3 or above) can deliver doses to a polar-cruising aircraft comparable to weeks of normal GCR exposure in a few hours. They are rare (typically a handful of S3+ events per 11-year solar cycle) and aircrew dispatch already includes SPE response procedures.

  As a passenger, you cannot meaningfully avoid SPEs through booking decisions. For frequent fliers, total lifetime contribution from SPEs is small relative to baseline GCR. See Solar particle events.

• Why is the public limit 1 mSv/yr if one transatlantic flight is 0.1 mSv?

  The ICRP-103 1 mSv/yr public limit applies to dose from controllable sources, practices subject to societal control like nuclear power generation. Cosmic radiation is explicitly excluded from the 1 mSv limit as a natural-background contribution. We nonetheless display the 1 mSv reference on the report because it is the most familiar benchmark of "small additional dose". The FAA's 6 mSv/yr aircrew action level (NCRP 132 / AC 120-61B) is the more directly comparable number for frequent fliers.

• Does the window seat matter?

  No. The cosmic-radiation field at cruise altitude is highly penetrating and broadly isotropic; the fuselage skin and the few inches of aluminium between a window and aisle seat make no measurable difference. Window vs aisle is a comfort question, not a dosimetry question.

• Does the type of aircraft matter?

  At the precision CARI-7 supports, no. Differences between common civil airframes at the same flight level on the same date are within the model's uncertainty band.

  What does matter is cruise altitude. A step climb from FL350 to FL410 raises dose rate roughly 15 to 25%. See Lower altitude = lower dose.

• Are the dose limits on the report regulatory limits I'm subject to?

  No, not as a passenger. The ICRP-103 1 mSv/yr public limit is an international reference, not a US regulatory cap on cosmic-radiation exposure. The 20 mSv/yr occupational limit applies to radiation workers under regulatory frameworks like 10 CFR 20; it is not US-regulated for aircrew, though the FAA recommends a 6 mSv/yr action level via AC 120-61B. Some EU member states do regulate aircrew under the EURATOM Basic Safety Standards Directive (2013/59/Euratom).

• Can I use this for a job-related dosimetry record?

  No. FlightRadiation reports are educational. They are not a certified dosimetry record. If you are aircrew and need a record for occupational-health or insurance purposes, your employer is recommended (in the US under FAA AC 120-61B) or required (in EURATOM jurisdictions) to provide one.

• How long until I get the PDF?

  Right away. The report is generated the moment your payment clears, usually within a few seconds, and you can download it immediately. A copy is also emailed to you.

• Do you store my flight details?

  We keep the route, altitude, and email you enter only as long as needed to generate and deliver the PDF, then delete them. We do not sell, resell, or share your details. We do not connect them to any identity beyond the email address you used to order.

Reviewed 24 May 2026 · Don't see your question? [email protected]