Step 1 : Introduction to the question "The jet stream blows in which direction?"
...Jet streams are fast flowing, narrow air currents found in the atmospheres of some planets, including Earth. The jet streams on Earth are westerly winds (flowing west to east). Jet streams are typically active at 20,000 feet to 50,000 feet, or about 7 miles above the surface and travel in what is known as the troposphere of Earth’s multi-layered atmosphere. The strongest jet streams are the polar jets, at 30,000–39,000 feet above sea level. Meteorologists use the location of some of the jet streams as an aid in weather forecasting.