Do commericial planes fly in the stratosphere?
The air in the stratosphere is very thin and not enough air pressure is available to provide the needed lift to support the airplane. The lower stratosphere can support some of the higher end spy planes such as the SR-71 spy plane, but commercial airplanes are not permitted to fly in the stratosphere.
The troposphere is the only atmosphere layer in which planes can sustain flight. Planes can fly as high as 7.5 miles (12 km) in the troposphere.
The stratosphere is as low as about 30,000 feet so commercial planes do cruise in the lower parts of the stratosphere. There’s an overlap between the two, as the troposphere can go from the ground to above 30,000 feet. Technically they do fly in the stratosphere but the stratosphere expands to above 150,000 feet.
