The jet stream is a fast-flowing, narrow current of air located in the upper atmosphere, typically around 7 to 12 kilometers above the Earth's surface. It flows from west to east in a narrow band and is driven by the temperature and pressure differences between air masses. The jet stream plays a key role in weather patterns and helps to transport moisture and energy across the globe. It can influence the intensity and direction of storms, as well as the development of weather systems. Scientists study the jet stream to better understand climate patterns, predict extreme weather events, and improve aviation safety.