What is the standard descent speed for aircraft?

The correct choice reflects the standard descent speed for aircraft, which is typically expressed in terms of Indicated Mach Number (IMN) or knots indicated airspeed (KIAS). For commercial jet aircraft, a standard descent speed of 0.74 IMN or 290 KIAS is a common practice during descent, as it provides a balance between fuel efficiency and safety while ensuring that the aircraft remains within operational limits. This speed allows for a smooth and stable descent profile while accommodating air traffic control requirements and maintaining adequate separation from other aircraft.

In contrast, other choices provide descent speeds that either exceed typical operational parameters or do not align with standard practices. Therefore, the selected answer is the most relevant in the context of standard operating procedures for aircraft during descent.