A control device (110, 900), comprising: an acquirer (191, 910) arranged to acquire weather information expressing weather related to a scheduled landing location at which a landing of an aircraft is scheduled, the weather including (i) a wind speed related to the scheduled landing location or (ii) a wind direction related to the scheduled landing location and the wind speed; a setter (192, 920) arranged to set an alert start condition in accordance with (i) the wind speed expressed in the acquired weather information or (ii) the wind direction and the wind speed that are expressed in the acquired weather information, the alert start condition being a condition corresponding to the weather and being a condition related to a positional relationship between the scheduled landing location and the aircraft; and a controller (193, 930) arranged to cause an alerter (180, 810, 980) to perform a behavior corresponding to the weather expressed in the acquired weather information, the alerter (180, 810, 980) being arranged to perform an alert related to the landing of the aircraft, the behavior corresponding to the weather including starting the alert at a timing at which the alert start condition is met, wherein: the alert start condition is a condition that a distance between the scheduled landing location and the aircraft becomes less than or equal to a set threshold, and the setter (192, 920) is arranged to set the threshold in accordance with the wind speed related to the scheduled landing location. an acquirer (191, 910) arranged to acquire weather information expressing weather related to a scheduled landing location at which a landing of an aircraft is scheduled, the weather including (i) a wind speed related to the scheduled landing location or (ii) a wind direction related to the scheduled landing location and the wind speed; a setter (192, 920) arranged to set an alert start condition in accordance with (i) the wind speed expressed in the acquired weather information or (ii) the wind direction and the wind speed that are expressed in the acquired weather information, the alert start condition being a condition corresponding to the weather and being a condition related to a positional relationship between the scheduled landing location and the aircraft; and a controller (193, 930) arranged to cause an alerter (180, 810, 980) to perform a behavior corresponding to the weather expressed in the acquired weather information, the alerter (180, 810, 980) being arranged to perform an alert related to the landing of the aircraft, the behavior corresponding to the weather including starting the alert at a timing at which the alert start condition is met, wherein: the alert start condition is a condition that a distance between the scheduled landing location and the aircraft becomes less than or equal to a set threshold, and the setter (192, 920) is arranged to set the threshold in accordance with the wind speed related to the scheduled landing location. the alert start condition is a condition that a distance between the scheduled landing location and the aircraft becomes less than or equal to a set threshold, and the setter (192, 920) is arranged to set the threshold in accordance with the wind speed related to the scheduled landing location.