It seems possible at this stage to judge which meteorological factors would be of most importance in commercial supersonic transport operations. The argument would be based on the possible data for the Concorde, which, as is well-known, will fly at mach 2·2 and for which the cruising altitude will be between 18 and 20,000 m. The mach 3 flight would have similar characteristics for which the cruising altitude would be 25,000 m. or more.