In spite of advances in technology, spatial disorientation (SD) continues to be a contributing factor in a large proportion of military aircraft accidents. Data from published reports of SD, and aircraft accident folders over the past three and one-half decades, were analyzed. The rate of major aircraft accidents per 100,000 flying hours decreased from 5.36 during the 14-year period of 1958-1971 to a rate of 2.22 during the 21-year period 1972-1992. During the same two time periods, however, the rate of SD caused major aircraft accidents per 100,000 flight hours remained approximately constant (0.32 and 0.35, respectively). Even though the average number of SD mishaps decreased from 23 per year in the 1958-1971 period to 12 per year in the 1972- 1992 period, the percent of SD accidents increased from an average of 6% during 1958-1971 to an average of 16% in 1972-1992. SD accidents still represent a major drain on USAF resources; but the development of helmet- mounted display technology provides an opportunity to present SD in some of the more demanding operational environments.