Speed control issues are considered for tunnel-in-the-sky displays with a predictor presenting guidance information in a 3-dimensional format for flight path control. Factors driving the predictor design are described. With reference to the resulting predictor control law, it is shown that the pilot-predictor-aircraft system is stable for operation on the frontside of the power-required curve and unstable for operation on the reverse. This instability can be removed by thrust control. It is shown that this control loop is supported by the predictor control law because of favorable coupling effects between the two loops involved. Furthermore, an appropriate speed indication in the tunnel-in-the-sky display is considered an aid in manual speed control. The theoretical findings are supported by experimental results from pilot-in-the-loop simulations.