Abstract: According to the latest regulations of CCAR93-R5, it is necessary to replace the abstract conditions of landing clearance issuance with practical timing points. The landing clearance issuing time algorithm under different conditions is proposed. Calculation employing B737-800 operation data shows that there are two checking points(7 km, 5 km) and one decision point (2.5 km) from the landing aircraft to the runway entrance. When landing aircraft approaching to the decision point, the controller can issue landing clearance under one of the following conditions: a) it is observed that the departing aircraft in front has lifted its front wheels and b) it is observed that the landing aircraft in front has entered the exit crossing without obstacles. Taking this result as reference, air traffic controllers can issue landing clearance with accurate timing, reducing runway incursion risk and aviation accidents.

Key words: landing clearance, issuing time, checking point, decision point, risk analysis