This study explored the propagation conditions of flight delays in different situations, including the same aircraft used for consecutive flights, the same gate used by various aircrafts and passenger transfer requirements between different flights. The study then derived the extent of flight-delay propagation, and established a set of delay-control strategies on controlling the propagation of the flight delays caused by incidents in the above three situations. In this study, knock-on delay propagations were defined and analyzed first, and then mathematical models were formulated to derive the extents of various flight-delay propagations according the characteristics of three different knock-on delays. Then, the study proposed a variety of feasible control schemes for controlling flight delay propagations, and evaluated these schemes by comparing time and costs for both airlines and travelers. Furthermore, how airlines can re-plan the buffer time to minimize the long-term flight delay propagation were discussed. Finally flight schedule and delay data on domestic Taipei-Kaohsiung flights of Airline C were collected. The models were applied to show their application and feasibility. The results showed that buffer time between flights affects flight delay propagation greatly, and flight-delay propagation will be serious if buffer-time is short. The results were reasonable as knock-on delay time and delay propagation range estimated by models were compared with those from past delay statistics. The adjusted buffer-time was shown to significantly improve the delay propagation problems for airlines, and verified the model’s usefulness and feasibility.