During the course of the Second World War, consideration was given to the means for operating post-war air routes. Concurrently, discussions were taking place as to the type and performance of the aircraft likely to be available. It was, however, quite obvious that, as we had had no previous experience at the higher altitudes at which these operations would be carried out, account would have to be taken of the winds which would be experienced, and steps were taken therefore to procure these data whereby to plan the routes.