The study aimed to investigate the efficacy of bright light intervention to improve behavioral alertness and reduce cognitive fatigue in flight crew-members. During the four week study, crewmembers wore actigraph bands to monitor sleep behaviors. Self-assessed levels of sleepiness were recorded using the Karlosinska Sleepinees Scale (KSS), and self-assessed fatigue was measured using the Samn-Perelli (SP) fatigue scale. Participants completed psychomotor vigilance tests (PVT) to measure behavioral alertness. On the third and fourth weeks of the study, participants were exposed to short wavelength bright light (465nm blue) light intervention. The results show that there was a significant difference in alertness and cognitive fatigue between pre-intervention and post-intervention for each crew member and that 39.1% of the variance is explained by time (pre/post intervention). There is also a significant difference in alertness between flight crew and cabin crew and 49.4% of the variance is explained by position (flight/cabin crew).