What does a square vertical flag (Hotel) signify?

The square vertical flag known as Hotel signifies that a pilot is aboard the vessel. This flag is part of the International Code of Signals, which is used to communicate important information quickly and effectively in maritime operations. When displayed, it indicates that the vessel is under the guidance of a pilot, who is responsible for navigating the ship through challenging areas, such as ports or narrow channels.

This communication is crucial for other vessels and shore stations, as it conveys that the ship is receiving local navigational expertise, which enhances safety and efficiency in congested or complicated waterways. The use of standardized flags like Hotel helps ensure that the importance of having a pilot aboard is acknowledged by other vessels and authorities, contributing to safer maritime navigation.