In an earlier paper, the writer attempted a quantitative study of a flow-planning system for aircraft intending to fly across Europe. This paper aims to offer each aircraft a clearance giving a reasonable expectation that, throughout cruising flight at least, there will be no conflict with other traffic. Such a clearance is sometimes termed a ‘tube of flight’. Reference i assumed a pattern of traffic flying along rhumb lines, each flight having a starting position chosen at random in a region roughly the size of Europe. Flight was in a random direction and the flight path length was chosen at random from a plausible distribution.
