Loading ...I have never tried a geiger counter in an airplane. I don’t need to. It is a known fact that pilots, flight crews, and passengers are subject to elevated cosmic rays (gamma and Xrays) at higher altitudes, because there is less atmosphere shielding them from what comes in from space. You can see the results of these measurement made by balloon here:
Scroll mostly down the page to: “Cosmic Rays in the Atmosphere” to see the seasonal changes in the readings. PLEASE NOTE… these measurements DO NOT “GO TO ZERO”. Please get that idea out of your head. You have been fed bad information. Geiger counters DO NOT ‘go to zero’ at high readings.