“…This problem is recognized to be very critical in Europe: the density of flights in the sky is often very high, and hence en-route congestion is a major constraint to the increase of air traffic. As for the ground holding problem, several algorithms have been proposed for solving the air traffic flow management problem, tackling networks of different complexities, and adopting either exact or heuristic strategies (Bertsimas et al, 2011;Patterson, 1998, 2000;Helme, 1992;Lindsay et al, 1993;Lulli and Odoni, 2007;Sherali et al, 2003Sherali et al, , 2006. Most of these algorithms are based, at least in some part, on integer programming models.…”