Cost estimation for alternative aviation plans against potential radiation exposure associated with solar proton events for the airline industry

In this paper, we present a systematic approach to effectively evaluate potential risk cost caused by exposure to solar proton events (SPEs) from solar flares for the airline industry. We also evaluate associated health risks from radiation using ExoKyoto, to provide relevant alternative ways to minimize economic loss and opportunity. The estimated radiation dose induced by each solar proton events (SPE) for the passengers of each flight is calculated using ExoKyoto and PHITS. We determine a few scenarios for the estimated dose limit at 1 mSv, and 20 mSv, corresponding to the effective dose limit for the general public and occupational exposure, respectively, as well as a higher dose induced an extreme superflare. We set a hypothetical airline shutdown scenario at 1 mSv for a single flight per passenger, due to legal restrictions under the potential radiation dose. In such a scenario, we calculate the potential loss in direct and opportunity cost under the cancelation of the flight. At the same time, we considered that, even under such a scenario, if the airplane flies at a slightly lower altitude (from 12 to 9.5 km, corresponding to the slight increase of atmospheric depth from 234 to 365 g/cm2), the total loss becomes much smaller than flight cancelation, and the estimated total dose now goes down from 1.2 to 0.45 mSv, which is below the effective dose limit for the general public. In the case of flying at an even lower altitude (7 km corresponding atmospheric depth with 484 g/cm2), the estimated total dose becomes much smaller, to 0.12 m Sv. If we assume the increase of fuel cost is proportional to the increase in atmospheric depth, the increase in cost becomes 1.56 and 2.07 for the case of flying at 9.5 km and at 7 km, respectively. Lower altitude flights provide more safety for the potential risk of radiation doses induced by severe SPEs. At the same time, since there is total loss caused by flight cancelation, we propose that considering lower flight altitude is the best protection against solar flares.