As there is apparently no expert in the world on “De-icing Runways from the Air”—and certainly not the author— the best start is to relate something of the difficulties of de-icing runways, the chemicals used and the rival methods of spreading them, and to leave it to the operators of agricultural aircraft to decide whether and how agricultural aviation can do a useful job in freeing runways from the menace of ice.

Clearly for the safety of landings and take-offs, runways should be kept clear of anything which reduces the coefficient of friction, whether this reduction is the result of plain wet, snow, ice or slush. It is the objective of the British Airports Authority in common with other airports, to remove precipitation so that one, to use the Canadian expression, “gets down to the black top”—even though one's runway is near-white concrete. When ice forms on an untreated runway, it is liable to key itself to the irregularities of the surface and become difficult to move. Therefore a good plan is to have deposited one's chemicals, when there is precipitation, before the temperature falls to freezing point or else early on in the fall before freezing is too firmly established. However, on occasions, precipitation, as everyone knows, occurs without being forecast or the temperature falls unexpectedly.