International Maritime Signal Flags

International Maritime Signal Flags Ships that pass in the night, and speak each other in passing, only a signal shown, and a distant voice in the darkness, Henry Wadsworth Longfellow, American Poet, 1807-1882 International marine signal flags are used by ships to spell out short messages, used individually or as part of a combination for a special meaning. For ceremonial and festive occasions ships can be dressed in marine signal flags with the flags strung from the rigging either end to end or bow to stern. Numeric pennants are also available in numbers 0-9. The triangular shape makes them easily discernible as being different from marine signal flags. Three code flag substitutes are available to repeat the first flag or pennant in the same hoist. The substitute flags are the same length but triangular in shape. Distress pennants are also available. There is one code flag answering pennant used to acknowledge a signal.

Marine Flags Standard Meanings

Code Flag A “Alpha” is used by diving support vessels to warn other boats that they cannot move and have a diver underwater so don’t approach. In yacht and dinghy racing, Code Flag P “Papa” is the preparatory flag to indicate a race is due to start and Code Flag S “Sierra” means the course has been shortened. Australian maritime flags

History of the International Marine Signal Flags

The International Code of Signals has a long history. The Code was drafted in 1855 by the British Board of Trade and published in 1857. The 18 signal flags were used worldwide from January 1901 and one year later was revised to 26 flags and a code pennant after the vowels and flags for letters X, Y, Z were introduced. The code was tested during WW1 and a new code of signals introduced in 1934. The International Code is maintained by the International Maritime Organization (IMO), an agency of the United Nations responsible for regulating shipping.

Semaphore Flag Signalling

The Semaphore Flag Signalling System is another alphabet system based on waving a pair of hand-held flags in a particular pattern. The square red and yellow flags are held at arm’s length in various positions to represent each letter of the alphabet. The positions resemble a clock face divided into eight positions for each of the left and right hands. Arms are kept straight when changing from one position to the next. semaphore flag signal


The Chart & Map Shop has all international marine signal flags and pennants available for sale. The high-quality, colourful screen printed code flags are 790 x 610 mm in size.


Before you go to sea, pick up your on-board reference Reeds Maritime Flag Handbook to read up on the different types of maritime flags, how they are made up, traditions, myths plus the dos and don’ts to using the flags. If a laminated card is easier to use onboard, pick up a copy of the A3 International Code of Signals. If you have any questions about maritime flags, don’t hesitate to call the experienced team at The Chart & Map Shop on 08 9335 8665, email or visit us in-store.
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