To improve the recognition probability of airborne infrared search and track systems (IRSTS) in air-to-air operations, the point target recognition probability model is established. And using an operating range model, the detection envelope is calculated for the airborne IRSTS. Combining with different operational backgrounds and specific technical parameters, the simulation results show that: (1) an increase in visual range and target speed, along with a decrease of oblique angle, produces an increase in the recognition probability; (2) the angle of maximum operating range of each detection envelope is the optimum detection point for the airborne IRSTS; and (3) the optimum threshold noise ratio is 8-10. These conclusions provide further scope in improving the operational effectiveness of airborne IRSTS in practical applications.