The aim of both teams is to tap into high-altitude wind, which is an energy source that is more abundant and reliable than the ground-level wind on which normal turbines depend.

The immediate cause of the problems is the behaviour of the jet stream, a band of high-level wind that travels east around the world and influences much of the weather below it.

Convective cells formed at high altitude plots firstly and then spread to lower altitude area, and the speed and directions of cells 'spread depend on terrain factors and upper level wind.