To accurately calculate the voyage of the aircraft with the track programmable capability from the takeoff to the destination, a simplified method of calculating the voyage is proposed. According to the characteristics of the flight path of the programmable aircraft, the flight calculation process is decomposed into the flight section and the cruise section, the aircraft in plane turning model, the vertical in plane program decline model and the cruise section of multi way road curve description mathematical model are established. The geometric method is used to give the calculation method of each voyage, and the proposed method is generalized to the complex trajectory with N waypoints. The system verification shows that the error between the calculated value of the aircraft range and the measured value of the aircraft navigation system is very small, and it has the characteristics of fast calculation and high precision.