At what altitude and time does CRZ thrust engage automatically?

The correct answer is the one that specifies engaging CRZ thrust at a preselected altitude for 90 seconds. This behavior is defined by the aircraft’s flight management system, which is designed to optimize performance during different phases of flight.

At the preselected altitude, the autopilot and thrust management systems work together to ensure that the aircraft stabilizes and maintains the desired flight profile. Engaging thrust in this manner allows for a gradual adjustments to be made, ensuring that the aircraft maintains an efficient cruise speed while remaining within operational and safety parameters.

The specific time of 90 seconds is significant because it gives the aircraft systems the necessary time to stabilize after reaching that preselected altitude, avoiding abrupt thrust changes that could compromise safety or passenger comfort.

Other options do not accurately capture this operational procedure. For example, engaging at any altitude for 60 seconds lacks the precision required for safe flight operations. Climbing through 10,000 ft alone does not account for when CRZ thrust engages, as it is more about achieving a stabilized climb and proper flight configuration rather than an automatic engagement at that specific point. Additionally, the notion that it only operates during cruise flight does not recognize the transitional phases that are essential in the climb to maintain optimal performance.