A computer-implemented method is described. The method is be implemented by processors of an aircraft system. The method includes receiving images of an eye and a lighting configuration associated with a cockpit of an aircraft. The method further includes detecting a position of the eye within each of the images. The method further includes compensating for a pupillary light response of the eye based on the position of the eye within the image and the lighting configuration. By compensating for the pupillary light response, a fatigue level of the operator is estimated with reduced noise.