The polar jet stream can travel at speeds greater than 100 miles per hour (160 km/h). Here, the fastest winds are colored red; slower winds are blue. Clouds along a jet stream over Canada. Jet streams are fast flowing, narrow air currents found in the atmosphere of some planets, including Earth.The main jet streams are located near the altitude of the tropopause. The major jet streams on Earth are westerly winds (flowing west to east).n each hemisphere, both upper-level jet streams form near breaks in the tropopause, which is at a higher altitude near the equator than it is over the poles, with large changes in its height occurring near the location of the jet stream.