Value: 5 Airplanes fly in which layer? \( \begin{array}{l}\text { a. Troposphere } \\ \text { b. Stratosphere } \\ \text { c. Mesosphere } \\ \text { d. Thermosphere }\end{array} \)

Airplanes primarily fly in the troposphere, which is the lowest layer of Earth’s atmosphere, extending from the ground up to about 8 to 15 kilometers (5 to 9 miles). This is where all the weather we experience occurs, and it’s also the layer where commercial air traffic operates, offering a balance of thin air for lift and enough density for engines to operate efficiently. In addition to the troposphere, some aircraft, particularly high-altitude jets or research planes, can ascend into the lower stratosphere, which starts around 10 to 15 kilometers above the Earth’s surface. The stratosphere is praised for its stability and lack of turbulence, making it an ideal cruising altitude for long-distance flights!