Air travel has transformed the way the world sees distance. Moving halfway round the globe often takes only a day. But airport congestion still brings more inconvenience than it should. Most aircraft journeys are smooth and seamless affairs. But transfer stops are still the bane of all long distance journeys. At best, the long distance passenger will wait an hour or so at a key hub airport. But if there are any delays at all on the schedule, the trip can become a nightmare. And probably the main culprit for delays is airport congestion.