Spatial disorientation (SD) is one of the most severe causative factors in aviation accidents. We analyzed the reported SD episodes to evaluate the characteristics of severe SD in fighter pilots. Three hundred seventeen cases (95.5%) of 332 total valid cases experienced SD, and the ratio of night and day SD experiences (52.7% vs. 47.3%) (p < 0.05) shows a clear prevalence of night SD events. The severity of SD episodes at night (2.23 +/- 1.09) was higher than at day (1.89 +/- 1.04) (p < 0.01). In addition, the severity of visual illusions was significantly higher at night. A significant difference was found for meteorological conditions, such as visual meteorological conditions (VMC), instrument meteorological conditions (IMC) and VMC-IMC (VI) transition, among times of days. In conclusion, the severity of the SD episodes was higher at night. This may be due to an increase in visual severe SD episodes at night.