In which IALA region may a buoy aid to navigation be lettered only and not numbered?

In the IALA (International Association of Lighthouse Authorities) system, the designation of aids to navigation varies by region, specifically Region A and Region B. In Region A, which includes Europe, Africa, and parts of Asia, buoys can be marked with letters only, while in Region B, which includes the Americas and parts of Asia, buoys typically have a system that employs numbers and colors along with the shapes.

Spherical buoys, being part of the designated aids to navigation in Region A, can indeed be lettered only. This allows for easier recognition and communication of navigational information in certain contexts where letters may serve to identify the buoys more clearly or in situations where space or visibility constraints limit the options for numbering.

Other buoy types, such as cylindrical, conical, and square buoys, typically follow the more standardized methods that incorporate numbering, particularly in Region B, where the mixed alphanumeric systems are prevalent to provide clearer navigation cues. Thus, the choice of a spherical buoy for the context of using letters only aligns with the IALA's regulation and intent to simplify navigation in specific areas.