INTRODUCTION: Loss-of-control (LOC) is the major cause of transport airplane mishaps. There have been many published reports and papers examining these accidents. While these studies did mention spatial disorientation (SD) as a cause or a factor, none of them analyzed it further. The present study uses transport and commuter airplane mishap data for a recent 35-yr period and examines the results of those mishaps involving spatial disorientation.METHOD: We identified LOC and SD accidents from five national aviation accident organizations and two independent groups. Only “normal” operations (air carrier, noncommercial transportation, ferry flights, and training) were considered. We reviewed transport and commuter airplane accidents using the published reports and identified 94 involving SD.RESULTS: We found the distribution of SD mishaps differs from LOC mishaps. During initial climb, there were relatively fewer SD mishaps (16%) than LOC mishaps (31%). During enroute climb SD has relatively more mishaps (18%) than LOC (11%). During go-around or missed approach phases, there were relatively more SD mishaps (21%) than LOC mishaps (4%). Perhaps the most significant observation was an increasing number of SD mishaps during the period reviewed.DISCUSSION: There are several possible reasons for the increasing numbers of SD mishaps over the study period from 1981 to 2016. Somatogravic illusion during go-around or missed approach accounts for only some of this increase. There is insufficient data to determine the reason for the remaining increase.Newman RL, Rupert AH. The magnitude of the spatial disorientation problem in transport airplanes. Aerosp Med Hum Perform. 2020; 91(2):65–70.