Introduction: visuospatial is a type of high-level visual perception necessary for identification, information integration, analysing of visual and spatial forms, details, structures and spatial relation. These functions are required in order to successfully complete aviation-related tasks, such as analysing movement, distance perception, and spatial navigation. The aim of this study is to examine whether hypobaric hypoxia can significantly influence changes in visuospatial function, thus increasing the risk of accident or serious incident during flight operation. Methods: this study is a quasi-experiment of pre-post study including before and after hypobaric hypoxia simulated through an altitude chamber. In this study, 42 military aircrews were exposed to different altitude zones at ground level, 10,000 ft (ft) and 25,000 ft respectively, for five minutes. At each altitude zone, the participants were instructed to complete a clock drawing test as a measurement for visuospatial function. The results were analysed using the McNemar non-parametric test. Results: among the 42 subjects, six show impaired visuospatial function at 10,000 ft and 26 participants show it at 25,000 ft. There were significant increased on the proportion of impaired visuospatial function between the ground level to 10,000 ft (p=0.031), 10,000 to 25,000 ft (p=0.0001) and ground level to 25,000 ft (p=0.0001). Conclusion: hypobaric hypoxia may have a significant influence on visuospatial function, starting from as early as 10,000 ft to 25,000 ft. This decrease of visuospatial function could affect human cognitive performance when flying and increase the risk of aviation accidents.