<div class="htmlview paragraph">The conclusions of an international airline following a series of detailed studies of a number of supersonic project designs are surveyed. It is pointed out that, to long-haul multiple stage carriers, the SST offers very real commercial advantages. Moreover, on balance, a timing of about 1970 for first service appears suitable.</div> <div class="htmlview paragraph">The economic lessons of the subsonic jet are also reviewed. It is concluded that the excessive size of the majority of the subsonic jets was the major factor in the economic crisis of the past few years. This error must be avoided with the SST.</div>