A longitudinal research project on stress and strain of helicopter pilots engaged in low-altitude night flight with night vision goggles (NVG) was carried out over 3 years. An overview is given regarding the design and theoretical background of the project. Psychological, physiological, and observational data were collected before, during, and after flight. In our theoretical model, stress and strain in flight result from concrete actions by specific pilots in specific objectively definable situations. Traits, such as anxiety, riskiness, and aggressiveness, are regarded as manifestations of behavior regulation styles, which appear during flight. These traits and behavior regulation patterns are determined by cognitive processes, especially the pilot's perception of himself and the situation. By identifying those characteristics of the person and the environment that (in an interaction) lead to critical flight situations and stress, it is possible to deduce weak points and give recommendations in the domain of flight security. As examples for concrete interactions between personality and situational variables, the observed stress of helicopter crews, which depends on the personality characteristics of riskiness and test anxiety (worry cognitions), and situation-characteristic difficulty are introduced.