Flags flown at sea serve several purposes. A house flag can help identify the owner or company that controls the ship. The ensign flag will reveal the nationality. A bungee shows the yacht club to which the ship belongs. Yet these nautical flags, while important, have not proved as helpful to those at sea as signal flags

A Brief History of Signal (Nautical) Flags

The International Maritime Flag System has one purpose: maritime communication. Signal flags have existed to pass signals between ships at sea, and between ships and people on shore. Records indicate that the Knights of Malta (founded in 1530). Yet it was not until 1857, that the British Board of Trade decided to publish a formalized version of the signals then in use. This is the International Code of Signals. Expansions of the Code in 1932 and 1969 facilitated its use in several different languages.


Originally, the system was comprised of 18 colored signal flags, capable of communicating a maximum of 17,000 different messages. The colors of these nautical flags were selected based on their visibility at sea. Today, they are composed of 40 flags in total. Twenty-six of them represent the letters of the alphabet and are square. Ten are numerical pendants. There is also 1 answering flag as well as 3 substitute flags. Together, these create an alpha-numerical language signaling system.

The combination of these nautical flags spells out the meaning given to it under the International Code of Signals. I can do so in several different languages including English, French, German, Greek, Italian, Japanese, Norwegian, Russian and Spanish.

Colors and Meaning

The colors of the signal flags are as follows:

  • Red
  • Blue
  • Yellow
  • Black
  • White

The signaling flags combine these colors on different shapes using different markings. A combination of 2 or 3 creates a specific message, however, a single flag is used to convey opposites – a common or urgent signal. In general, the following method applies:

  • Two-flags – maneuvering or distress signals
  • Three-flags – standard times, points of the compass, verbs, relative bearings, punctuation
  • Four-flags –names of vessels
  • Five –flags – position, time

All flags can also be used. This has nothing to do with communication but everything to do with a celebration. For such an event, mariners will string these nautical flags from the rigging in a “bow-to-stern” direction.

Nautical flags come in many different forms and shapes. They all help identify some aspect or character of the ship. Yet, signal flags are the ones that play a very important role in the past and present history of maritime communication.