Describe jet streams by using the information in the reading, and provide examples of the way that they affect air travel by drawing on the material that you heard in the lecture.

According to the passage, a jet stream is an irregular stream of weather that occurs in high altitudes, near the top of the Earth's troposphere. It blows with a speed of at least 57 miles per hour. The main causative factor of such wind patterns is the difference between the temperature of polar and tropical areas that leads to air flows from colder to warmer places. Hence, the winds are stronger in cold seasons. There are two main streams over the North America: the subtropical and the polar. The direction of jet streams is generally from west to east.

The professor explains that the polar jet stream separates the cold polar weather from that of the warmer southern regions. Thus, the stream blows from polar and Canadian areas to Texas and Mexico in warm seasons, while in colder times of the year the streams retreat. In order to illustrate his point, the professor mentions the flights between New York and Los Angeles.

He says that flight from Los Angeles to New York will take one hour lesser that the return flight. This is because of the west to east direction of the jet streams. Therefore, the plane glides over the stream. However, in return flight, the plane should fly against the wind current, which the passage says that has an average core speed of 190 miles per hours. The professor further argues that due to less resistance from the air currents against the plans' wings the flight from Los Angeles to New York consumes less fuel. Moreover, he suggests that the jet stream can have additional influence on air travels by changing the weather of the destination.