II—Jet Streams and the Pilot

Extract

In the early days of civil aviation, aircraft flew too low to encounter jetstreams. Later they were no doubt encountered, when aircraft were flying at medium heights of from 10,000–20,000 ft.; however, the infrequency of astro fixing in those days would generally disguise a high-velocity wind by meaning it with low-velocity winds, producing resultant winds of medium velocity. Occasionally, however, very high winds would be experienced and the unexplained displacement of position would be attributed to a navigational error or some other cause of that nature.