From the very few tables I am able to find, it seems that for flights at altitudes lower than about 10 kilometers ( 33,000 feet) the exposure isabout the same and independent of latitude. You get about 5 millirems which is slightly lower than a single chest X-ray ( 8 millirems) and vastly lower than your dose from all natural sources on the surface ( 300.00 millirems). Only at altitudes above 15 kilometers ( 50,000 feet) does the dosage become interesting ( 60 millirems ). Below 10 kilometers, the rate is not affected by solar activity because of all the atmospheric shielding. Also, your jet hasa bit of shielding too.

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