Abstract: Guiding an aircraft to follow a four-dimensional flight path during a descent with a nominal thrust setting corresponding to idle thrust or non-idle thrust includes monitoring actual along-track position and actual vertical position of the aircraft relative to corresponding desired positions on the flight path, generating control commands based on deviations of the actual vertical position of the aircraft from the desired vertical position, and generating elevator commands based on the deviation of the actual along-track position from the desired along-track position, wherein generating control commands includes, if the deviation of the actual vertical position from the desired vertical position indicates that the aircraft is too low, generating a throttle command to increase the thrust setting to above nominal thrust, and generating a speed brake command to deploy speed brakes when the deviation of the actual vertical position from the desired vertical position indicates that the aircraft is too high.