THE SST project is the largest, most expensive and most dubious project ever undertaken in the development of civil aircraft. It is dubious because of the concern about the side effects of supersonic flying on a regular basis, the main one being the sonic boom. Apparently the more one learns about the sonic boom, the more intractable it appears.

The project is unique in that in Europe it was instigated by, and financed by, the Governments for airlines and not by airlines. A similar, although not exactly the same, pattern is followed in the USA.

Another main characteristic of the SST is that no airline has ever asked for it, but the project existing has tempted a few airlines to put in tentative orders, which has encouraged other airlines out of fear to put in other orders.

The general run of technical unknowns is pretty well-known, one of them being how to get rid of the heat caused by the friction of the air at the high speeds involved. However, probably the greatest doubt lies in the improbability that the SST will be able to be profitable in operation. I agree that it is possible to make any given number of calculations on this matter, all with reasonable degrees of honesty, and half of them will show that airlines will make money and the other half will show the opposite. This is merely a measure of our lack of knowledge of these aircraft.