The passenger door, emergency door and other doors of civil aircraft are mostly designed semi-plugged, of which some marginal structures, such as guiding shaft and doorstop, exceed the net opening of the door frame. When subject to positive pressure, the doorstops compress the matched stops on the door frame, meanwhile the guiding shaft and the guiding groove should maintain sufficient clearance to ensure that the pressurized load is transferred to the fuselage only through the doorstops. In the failsafe loading condition, since one of the doorstops is damaged, the deformation may make the shaft and the groove contact, thus a portion of load is transferred through the contact which greatly depends on the gap size. The gap is usually ignored in traditional failsafe analysis, and it is considered that the adjacent shaft definitely bears a part of the load after the stop is damaged. In this paper, the failsafe analysis on the semi-plugged door using linear gap element in Nastran as well as the analysis without considering the gap was given, the comparison and discussion demonstrate the significance of using the linear gap in failsafe analysis, and the effect of the design gap on the load distribution was further revealed, the design basis of the key load-carrying components of the aircraft doors was presented from the perspective of mechanics.