© The Author(s) 2020. Published by Oxford University Press. All rights reserved. For Permissions, please email: email@example.com.In this study, cosmic radiation doses were calculated for domestic and international flights departing from Istanbul and furthermore for domestic flights departing from Ankara using a software program called CARI-7A and also a mathematical method approach. Main parameters for calculating cosmic radiation are vertical cut-off rigidity, flight duration, latitude-longitude and altitude of the flight. Our calculation results agree with the measurements for domestic and international flights departing from Istanbul and Ankara.