Scientists at the Australian National University in Canberra have found that wind shear produced by solitary atmospheric waves is a potentially serious hazard to aircraft operating at low altitudes. In recent years a significant number of aircraft accidents have been attributed to a sudden, unexpected encounter with low-level wind shear during the landing or takeoff stage. In many cases it has been possible to associate the hazardous shear with one of a variety of well known meteorological wind shear conditions including intense thunderstorm down drafts, down-draft-produced density currents, cold frontal systems, and sea breezes. These sources are easily recognized and are usually predictable in the airport environment. In some instances, however, the identity of the wind shear source has been uncertain. Studies of the properties of large amplitude solitary waves in the boundary layer have shown that they produce intense, transient, horizontal and vertical wind shears which are comparable with the well known types of shear. Solitary wave activity may therefore account for some hitherto unexplained aircraft accidents.