When is a qualified clearance issued for an approaching aircraft?

A qualified clearance for an approaching aircraft is typically issued when the preceding aircraft has been given assurance that it will clear the runway in time to allow for the landing of the next aircraft. This means that the air traffic controller has determined that the first aircraft will vacate the runway in a timely manner, ensuring safety for the incoming aircraft.

In air traffic scenarios, ensuring that there is no conflict between the two aircraft is crucial for operational safety and efficiency. When the controller assesses that the preceding aircraft will clear the runway—meaning it is either in the process of taking off, landing, or taxiing away from the runway—the subsequent aircraft can be cleared to approach or land without undue delay or risk of collision.

The other situations in the options pose issues for clearance. For example, if the preceding aircraft is still in the air without a clear expectation of when it will land, or if it's on the ground but not moving away from the runway, issuing a clearance could potentially result in unsafe conditions. Therefore, the condition of the preceding aircraft directly influences the issuance of a qualified clearance for the arriving aircraft, making the clearance valid only when the preceding aircraft is expected to clear the runway properly.