In this paper, two methods of fatigue load calculation, the aeroelastic model and the simplified load model (SLM) defined in IEC61400-2 Ed.2, are compared. Because the SLM does not include the effect of braking, the SLM overestimates the fatigue load under high wind speeds. It is also revealed that the design wind speed, which is used in the SLM, is not necessarily representative of the fatigue load. Finally, a modified SLM shows a sensitivity to the wind that is similar to that of the aeroelastic model.