Hotel Flag
F5. The Reference Layer: Glossary, Units, Signals and Information SourcesDefinition
International Code of Signals letter H, meaning "I have a pilot on board."
Split vertically, white at the hoist and red at the fly, Hotel is letter H of the International Code of Signals, meaning “I have a pilot on board.” A ship hoists it singly to tell traffic and shore stations that a pilot is conning the vessel through pilotage waters. It is the natural sequel to Golf, which requests a pilot; together the two flags mark the start and progress of a pilotage transfer.
Source: International Code of Signals (IMO, 1965 edition as amended), single-letter signal H.