What happens to engine thrust output above 36,000 ft?

At altitudes above 36,000 feet, engine thrust output decreases primarily because of reduced air density and the resulting effects on combustion and airflow through the engine. As altitude increases, the density of air decreases significantly. This lack of available oxygen can hinder the combustion process, which is essential for generating thrust.

Even though the temperature might remain stable, the key factor here is the reduction in air density. Engines rely on the intake of air to mix with fuel for combustion, and with less air available, the engine produces less thrust. This phenomenon is particularly pronounced in turbojet and turbofan engines, as they are designed to operate efficiently at lower altitudes where air density is greater.

Because of these dynamics, maintaining a consistent thrust output at such high altitudes becomes challenging, leading to a noticeable decrease in engine performance. Understanding this relationship between altitude, air density, and engine thrust is critical for pilots and engineers involved in aircraft operations and design.