Which statement best reflects when the critical phase of flight begins with respect to altitude during climb/descent?

• A. The phase includes 1000 ft prior to reaching assigned altitude
• B. The phase begins only at takeoff
• C. The phase begins at cruise altitude
• D. There is no defined altitude-based phase

Answer: (A)

During climb and descent, the phase where workload and aircraft control are most demanding centers on your proximity to the assigned altitude. The standard approach defines the critical phase as the portion within about 1000 feet of the target altitude, so the last 1000 feet of climb and the segment approaching the assigned altitude during descent are considered critical. This framing helps ensure heightened crew attention and tighter procedures precisely when altitude accuracy matters most.

So the statement that the critical phase includes the final 1000 feet before reaching the assigned altitude is the best fit. It isn’t limited to takeoff, it isn’t defined by cruise altitude, and there is indeed an altitude-based boundary used to identify this phase.