The Cairo-Cape flights of 1920 brought into prominence many peculiarities of conditions arising from the high temperature combined with high altitude ot the aerodromes on the route. The conditions were for the most part new, for flight from elevated aerodromes in Europe and the United States has been made as a rule in temperate climates, where the temperature at such altitude was low. These peculiarities, which led to great difficulties for the pilots, may be divided into two classes :—

(1) Engine peculiarities, especially defects of carburation and unequal heating of the cylinder jackets owing to the high temperature of the air.

(2) Aerodynamical peculiarities, owing to the tenuity of the atmosphere. In the former class the difficulties were not to be foreseen, and much valuable information has been obtained as a result of these flights.

The latter class of difficulty, on the other hand, was one that could have been predicted with certainty by anyone who has had experience in the testing of the performance of aeroplanes under varying conditions of the atmosphere.