Much work has been done on compressible flow since the contribution of the Aerodynamics Division to research in this field was last described to the Society by the late C. N. H. Lock in 1937. At that time he was able to review many of the data which were available from other sources, whereas today such a task would be impossible in a paper of this length. We shall confine ourselves here, therefore, to a description of some of the experimental work that has been done during the past few years in the high-speed laboratory of the Division, and to an account of the lines along which it is intended to continue the work in the future.

An opinion exists, more felt than written or spoken, that safety standards in air transport do not keep pace with technical progress. The facts belie this and, given a united effort by all concerned, there should be opening up a period of increased safety.

A simple comparison of the characteristics of say, the Ensign class with more modern aircraft, cannot reveal progress, and might even show the reverse. Commercial competition, operational demands, and public expectations have taken us beyond the stage when we can think in terms of the aeroplane alone and have led to the present state when air safety can only be examined in terms of the aircraft associated with ground equipment and airline organisation.

The role of meteorology in air operations is becoming increasingly important and an understanding of meteorology is desirable in the consideration of a number of the problems to be faced. The forecasting of winds en route and the use of these forecasts is one such problem, which has been brought into greater prominence by the advent of fast, high-flying aircraft. A great deal of work is being done on upper air winds and it is already clear that curious and significant phenomena sometimes occur. Thus very high winds are sometimes found in belts of limited lateral extent—the so-called “jet stream.” Not only high winds, but high rates of change of wind occur in such regions and they are clearly a potential source of difficulty to the navigator. Apart from the jet stream —a meteorological highlight of recent development—airline operators are also concerned with the problem of route planning.