At what altitude does the standard temperature lapse rate typically apply?

The standard temperature lapse rate of approximately 2 degrees Celsius per 1,000 feet is typically considered to apply up to 36,000 feet in the troposphere, but for practical aviation purposes, it is often referred to in the context of the first 18,000 feet. This layer is significant because it includes the majority of general aviation operations, where pilots must understand how temperature changes with altitude affect aircraft performance.

The concept of the lapse rate is essential for pilots, as temperature directly influences air density and, consequently, aircraft performance metrics such as lift and engine efficiency. Pilots calculating performance charts or flight planning need to account for these changes in temperature to ensure safe operation.

While the lapse rate may continue with less predictable variations beyond 18,000 feet, it is the standard atmosphere that pilots primarily use for altitudes within this range. Therefore, at 18,000 feet, the lapse rate remains stable enough to be applied reliably, making it the correct choice for this question.