Galactic cosmic-ray-induced air showers constitute the largest source of radiation exposure for aircrew and passengers. To facilitate the evaluation of effective doses received by this population, a database containing dose rates of various radiation components in the atmosphere was established; the parameterization accounted for altitude, geomagnetic rigidity and solar modulation. Energy spectra of secondary cosmic rays and effective dose rates were calculated using the FLUKA Monte Carlo code. An auxiliary MATLAB program with a graphical user interface was developed to estimate the aviation route dose through interpolation and integration. The dose calculator was benchmarked by comparing its predictions with data from other assessments. Finally, a set of representative flight routes of substantial interest in Taiwan was selected and evaluated.