<P> Jet streams are the product of two factors: the atmospheric heating by solar radiation that produces the large scale Polar, Ferrel, and Hadley circulation cells, and the action of the Coriolis force acting on those moving masses . The Coriolis force is caused by the planet's rotation on its axis . On other planets, internal heat rather than solar heating drives their jet streams . The Polar jet stream forms near the interface of the Polar and Ferrel circulation cells; the subtropical jet forms near the boundary of the Ferrel and Hadley circulation cells . </P> <P> Other jet streams also exist . During the Northern Hemisphere summer, easterly jets can form in tropical regions, typically where dry air encounters more humid air at high altitudes . Low - level jets also are typical of various regions such as the central United States . There are also jetstreams in the thermosphere . </P> <P> Meteorologists use the location of some of the jet streams as an aid in weather forecasting . The main commercial relevance of the jet streams is in air travel, as flight time can be dramatically affected by either flying with the flow or against, which results in significant fuel and time cost savings for airlines . Often, the airlines work to fly' with' the jet stream for this reason . Dynamic North Atlantic Tracks are one example of how airlines and air traffic control work together to accommodate the jet stream and winds aloft that results in the maximum benefit for airlines and other users . Clear - air turbulence, a potential hazard to aircraft passenger safety, is often found in a jet stream's vicinity, but it does not create a substantial alteration on flight times . These are narrow belts . </P> <P> After the 1883 eruption of the Krakatoa volcano, weather watchers tracked and mapped the effects on the sky over several years . They labelled the phenomenon the "equatorial smoke stream". In the 1920s, a Japanese meteorologist, Wasaburo Oishi, detected the jet stream from a site near Mount Fuji . He tracked pilot balloons, also known as pibals (balloons used to determine upper level winds), as they rose into the atmosphere . Oishi's work largely went unnoticed outside Japan because it was published in Esperanto . American pilot Wiley Post, the first man to fly around the world solo in 1933, is often given some credit for discovery of jet streams . Post invented a pressurized suit that let him fly above 6,200 metres (20,300 ft). In the year before his death, Post made several attempts at a high - altitude transcontinental flight, and noticed that at times his ground speed greatly exceeded his air speed . German meteorologist Heinrich Seilkopf is credited with coining a special term, Strahlströmung (literally "jet current"), for the phenomenon in 1939 . (Modern German usage is "Strahlstrom".) Many sources credit real understanding of the nature of jet streams to regular and repeated flight - path traversals during World War II . Flyers consistently noticed westerly tailwinds in excess of 100 mph (160 km / h) in flights, for example, from the US to the UK . Similarly in 1944 a team of American meteorologists in Guam, including Reid Bryson, had enough observations to forecast very high west winds that would slow bombers going to Japan . </P>

Who needs to know about the jet stream