When the behavior of an automated system deviates from an operator’s expectations, a surprise effect may occur, potentially compromising operational safety. An analysis of the U.S. Aviation Safety Reporting System (ASRS) database identified 281 instances of pilot surprise events triggered by automated systems. A systematic review of these incidents revealed that higher degrees of automation (DOA) are susceptible to the surprise effect. Additionally, drawing on these incidents and existing literature, we investigated the mechanisms through which DOA contributes to the occurrence of surprise effects from both human and machine perspectives. Finally, we underscore the importance of addressing the potential safety risks posed by high DOA within the aviation industry.