It should be pretty clear, then, that if ground-based travel alternatives gets improved in regards to speed and comfort, this would be a real boon to air travel as well. If air travel loses passengers to ground transportation on some shorter routes, some airports would be less busy, there would be fewer flights, and it would be a let-up in this development towards waits for time slots and long holding patterns when landing. You can behold a long, illuminated ribbon of aircrafts awaiting their turn to land. And air traffic is growing rapidly. Considering that some aircrafts will be discarded because of old age, there would still be a growth of about 700 new aircrafts in the sky every year.
Air traffic is no small threat to the environment, as well.
Exhaust fumes released at those altitudes where inter-continental flights travel might well influence the hothouse effect. Only, beam systems on the ground can do so much more efficiently. Well, the obvious reason is that aircrafts need so much space on all sides, for safety reasons. Also, they are confined to travel corridors, because they travel between airports, and these corridors cannot handle more traffic than can be handled by the airports at each end. In year 2002, the permitted vertical distance between aircrafts in Western European flight corridors will be reduced from 600 meters to 300 m.