There is provided a passive module for a holding structure. The holding structure is adjacent or part of a movable wing. The passive module comprises a support structure. The passive module comprises a radio transmission regulating structure. The radio transmission regulating structure is supported by the support structure. The radio transmission regulating structure has a radio transmission regulating characteristics. There is also provided a holding structure. The holding structure exhibits a slot for receiving such a passive module. There is further provided a kit of parts comprising at least one such passive module and such a holding structure.