Maritime signal flags

Maritime signal flags are a visual communication system used by ships to convey standardized international messages.

About this subject

Maritime signal flags form an international code of communication between vessels, dating back to the 19th century. Each flag represents a letter of the alphabet or a specific meaning, such as danger, need for medical assistance, or maneuver. The International Code of Signals (ICS), established in 1855 and revised by the International Maritime Organization, standardized 26 letter flags, 10 numeral pendants, and 3 repeaters. Colors and patterns are chosen for maximum visibility at sea: red, yellow, blue, black, and white predominate. In regattas, flags indicate starting procedures or weather conditions. Despite radio and satellite communications, flags remain mandatory for merchant and naval vessels, used in ceremonial occasions or as communication backups. A curious fact: the 'Z' flag, yellow and black striped, means 'I require a tug' in the ICS code.

Frequently Asked Questions

How many flags are there in the International Code of Signals?

There are 26 letter flags, 10 numeral pendants, and 3 repeaters, totaling 39 flags, plus special flags such as the answering pennant.

Which flag means 'danger'?

Flag 'O' (yellow and blue divided diagonally) means 'Man overboard', while flag 'U' (red and white quartered) means 'You are running into danger'.

Are maritime flags still used today?

Yes, especially for ceremonial communications, in regattas, and as a backup system for merchant and naval vessels.