The angle of attack (AOA) of an airplane is calculated as the difference of the flight-path angle and the pitch angle. The pitch angle is available from an attitude monitoring device (e.g., pitch gyro), but the flight-path angle is not available from the basic instruments common in general aviation. This method determines the flight-path angle mathematically, and in particular, using inputs from indicated airspeed and GPS. The sine (trig function) of the flight-path angle is the value determined by dividing the vertical velocity, provided by onboard GPS, by the velocity along the flight path (e.g., indicated airspeed). The sine value is converted to the value of flight-path angle by referring to a sine lookup table.