Effects of speed reduction in climb, cruise and descent phases to generate linear holding at no extra fuel cost

Speed reduction strategies have proved to be useful to recover delay if air traffic flow management regulations are cancelled before initially planned. Considering that for shorthaul flights the climb and descent phases usually account for a considerable percentage of the total trip distance, this paper extends previous works on speed reduction in cruise to the whole flight. A trajectory optimization software is used to compute the maximum airborne delay (or linear holding) that can be performed without extra fuel consumption if compared with the nominal flight. Three cases are studied: speed reduction only in cruise; speed reduction in the whole flight, but keeping the nominal cruise altitude; and speed reduction for the whole flight while also optimizing the cruise altitude to maximize delay. Three representative flights have been simulated, showing that the airborne delay increases significantly in the two last cases with nearly 3-fold time for short-haul flights and 2-fold for midhauls with the first case. Results also show that fuel and time are traded along different phases of flight in such a way the airborne delay is maximized while the total fuel burn is kept constant.