A great deal has been said and written about the necessity to launch into a completely new standard plateau of systems engineering for supersonic, as distinct from subsonic, aircraft. So far as I have been able to gather, one reason for all this could be the argument that, as the supersonic aircraft will be so costly to operate, i.e. so uneconomical, it must be operated at a very high utilisation with very short turn-rounds and that therefore all the systems must be very much more durable than has previously been the case. Another reason could well be that the flight régimes are such that there will have to be much more dependence on certain systems, e.g. pressurisation at 70,000 ft., cabin cooling at very high speed and so on.