What part of the atmosphere do helicopters fly in?

Helicopters primarily fly in the troposphere, which is the lowest layer of the Earth's atmosphere, extending from the surface up to about 8 to 15 kilometers (5 to 9 miles) in altitude. This layer contains most of the atmosphere's mass, including weather and clouds, making it suitable for helicopter operations. Helicopters typically operate at altitudes ranging from a few hundred feet to several thousand feet, well within the troposphere.