Most of us think of congestion in terms of that seen at airports around the world several times a day. However, out of sight is definitely not out of mind and perhaps the biggest problem facing long haul airlines in the future will simply be operating the required number of aircraft in what is rapidly becoming very confined airspace as the world's primary airways begin to reach saturation. The other benefit of the new system will be to allow airlines to flight plan flexible tracks that not only keep them apart from one another but also maximise their ability to use tailwinds and avoid thunderstorm cells, etc. (Rob Finlayson)