The following contributions are selected from contributions to the discussion on Wing Commander E. J. Dickie's paper ‘The Effective Use of Airspace’. The paper was presented at an Institute meeting held in the Royal Geographical Society's house on 21 March, and is printed in the last number of the Journal.

I remember on many occasions in my Service experience undertaking cross-country flights with a large number of other aircraft flying along exactly the same route at almost precisely the same time. These were usually navigation training flights and, therefore, to some extent the errors which arose might not be held to be representative of what one would expect to happen to seasoned airline operators. Nevertheless, it was a commonplace to find on such occasions, very shortly after taking off, that all aircraft became so scattered as often to disappear from each other's view completely. And yet, at each turning point and again at the destination they all arrived at the same time. I am sure that there is something to learn from this particular aspect of flight along identical or parallel tracks. I do not think a simple fore-and-aft radar indicator would provide the safety in flight which we are anxious to establish. I believe that a secondary radar, giving an all-round horizontal view, would probably go a long way to meet the stated requirement; although, of course, only one giving a spherical view could give 100 per cent safety. Even with pilots who can see exactly where they are going, along clearly defined tracks over country abounding in natural navigational aids, it is true to say that the really effective variable is the track and not the timing. This lateral scatter is due to inaccurate steering data and to the many other inaccuracies affecting the actual path of an aircraft through the air, quite apart from wind-finding errors. Even with the best primary navigational aids, tracks cannot be flown with absolute precision. It follows that collisions are at least as likely to arise from errors of track as from errors of timing. So I would suggest that what we really need is a secondary radar which will give us an all-round horizontal view and I think that we must not delude ourselves into thinking that even the finest primary navigation aid will provide an accuracy in the air by which all aircraft proceeding along one route will remain only fore-and-aft of each other.