What is the correct phraseology for issuing a landing clearance to an arriving aircraft that has not been visually observed?

The phraseology for issuing a landing clearance to an arriving aircraft that has not been visually observed must include a specific statement that indicates the aircraft is not in sight. This is important for clarity and safety, as it informs the pilots that they are cleared to land even though they cannot see the runway or the tower's visual confirmation.

The choice “NOT IN SIGHT, RUNWAY 28R, CLEARED TO LAND” effectively communicates to the pilot that while the tower does not have visual contact with the aircraft, they are still cleared to land on that specific runway. This phraseology aligns with established aviation communication protocols, ensuring that all parties have a clear understanding of the landing clearance under circumstances where visual observation is lacking.

The other options do not convey the same level of clarity regarding the visual situation of the aircraft. For example, simply stating "CLEARED FOR LANDING" or "LANDING APPROVED" does not indicate the status of visual observation, which could lead to misunderstandings or potential safety concerns in an operational environment. Thus, the chosen phraseology not only follows standard procedures but also enhances safety by providing critical information to the pilot.