This study aims to analyze the crosswind resistance ability of aircraft considering the crosswind gradient. To accurately depict the dynamic behavior of aircraft operating under gradient wind conditions, a refined six-degree-of-freedom nonlinear model is proposed. The study discusses three commonly used crosswind landing correction methods: sideslip crosswind technique, crab crosswind technique, and crab and sideslip combined technique. Building upon this, the concept of the flight feasibility region is introduced to analyze these three landing approaches. Furthermore, the equilibrium capability of aircraft under gradient crosswind conditions is investigated based on the proposed model. A case study using the B737 aircraft is conducted, revealing a significant impact on the aircraft’s feasible flight region with increasing wind field gradient. Neglecting the wind field gradient can potentially compromise the landing safety of the aircraft.