A single chime at ____ feet indicates the beginning of the sterile flight deck for descent.

• A. 5,000 feet
• B. 10,000 feet
• C. 15,000 feet
• D. 20,000 feet

Answer: (B)

The idea being tested is when crews switch to sterile cockpit operations, where nonessential talk is minimized to keep attention on flight tasks during critical phases. A single chime is used as a cue to begin this sterile period during descent, and the established trigger is at 10,000 feet. As you descend from cruise toward approach, the workload focuses on configuring the aircraft, managing speed and descent profile, and coordinating with ATC. Starting sterile conditions at 10,000 feet helps ensure the crew isn’t distracted during this transition and the approach sequence. The other altitudes don’t serve as the standard cue for beginning sterile operations during descent, because they occur either well above the transition to approach or well within the late descent/landing period.