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.