  The diverse near-Earth radiation environment due to cosmic rays and solar
radiation has direct impact on human civilization. In the present and upcoming
era of increasing air transfer, it is important to have precise idea of
radiation dose effects on human body during air travel. Here, we calculate the
radiation dose on the human body at the aviation altitude, also considering the
shielding effect of the aircraft structure, using Monte Carlo simulation
technique based on Geant4 toolkit. We consider proper 3D mathematical model of
the atmosphere and geomagnetic field, updated profile of the incoming particle
flux due to cosmic rays and appropriate physics processes. We use
quasi-realistic computational phantoms to replicate the human body
(male/female) for the effective dose calculation and develop a simplified
mathematical model of the aircraft (taking Boeing 777--200LR as reference) for
the shielding study. We simulate the radiation environment at the flying
altitude (considering geomagnetic latitude in the range of 45-50$^{\circ}$), as
well as at various locations inside the fuselage of the aircraft. Then, we
calculate the dose rates in the different organs for both male and female
phantoms, based on latest recommendations of International Commission on Radio
logical Protection. This calculation shows that the sex-averaged effective dose
rate in human phantom is 5.46 $\mu$Sv/h, whereas, if we calculate weighted sum
of equivalent dose contributions separately in female and male body: total
weighted sum of equivalent dose rate received by the female phantom is 5.72
$\mu$Sv/h and that by the male phantom is 5.20 $\mu$Sv/h. From the simulation,
we also calculate the numerous cosmogenic radionuclides produced inside the
phantoms through activation or spallation processes which may induce long-term
biological effects.
