A Glossary of Military Terminology, Jargon, and Slang
compiled and edited by Jeff Crowell

Nautical Signal Flags

Signal Flags

U.S. Navy / NATO / International

The following table shows the flags and pennants typically used in U.S. Navy ships for visual signaling and gives basic explanations of their meanings. A comprehensive explanation of the meanings of these flags is far beyond the scope of this FAQ – the publications used to encode, decode, and interpret flag signals (the NATO Allied Tactical Publications – ATP-1A and B) comprise two binders, each about three inches thick!

In a formation one ship is designated the Guide, and all ships will take their stations relative to this vessel. The Guide flies the Golf flag. The Guide may or may not be the ship from which tactical (maneuvering) signals are sent. The Guide may change throughout an evolution or series of signals. All ships in company generally carry the Golf flag closed up (hoisted all the way to the yardarm) at the main, on centerline, but with the flag rolled up and tied with twine so that it cannot be seen. That way, if your ship is designated the Guide, all you do is give a sharp tug to the halyard, the twine breaks, the flag unfurls, and you're now the Guide. And you've looked sharp and seamanlike to boot.

A complete signal may comprise one or many flags. A limited number of flags can be accommodated on a single halyard, so a complete signal may take more than one halyard, but it is also possible to have more than one signal in a single hoist. One halyard of flags, whether a single flag or many, is called a hoist. When a signal must be broken into multiple hoists, it must be divided at such a point that the meaning is not changed. A complete signal or group of signals – whether on one hoist or on two or more adjacent hoists flying at the same time – is called a display. When displays of more than one hoist are raised, the separate hoists are run up, one by one, in the order they are to be read. A hoist of flags is always read from the top down; when multiple hoists are displayed, the signal is read top down, outboard to inboard, and from forward to aft. As a rule, a signal too long to be shown completely on three halyards is made into two or more displays. When two or more displays are used, the heading (the initial part of the signal) must be hoisted on a separate halyard and kept flying while successive displays are made. When several hoists are displayed simultaneously from different points, they are read in the following order: (1) masthead; (2) triatic stay (a line run between masts or from masthead to stack, etc.); (3) starboard yardarm; (4) port yardarm. Signals hoisted at yardarms of different heights are read beginning with the tallest.

A typical flag signal is raised at the dip (not fully raised up the halyards) by the ship which has the OTC (Officer in Tactical Command) embarked. All ships in the formation read the signal. Each ship's signals gang bends on exactly the same signal, and hoists it at the dip. This signifies that the ship has correctly read the signal (much embarrassment results if a ship hoists an incorrect version of the signal). As each receiving ship breaks (decodes) and understands the signal, it fully raises, or closes up, the hoist to show that it understands and is ready to carry out the orders and maneuvers implied by the signal. Once all receiving ships have closed up the signal, the OTC closes up the signal to indicate prepare to execute. Execution of the signal occurs when the OTC briskly hauls down the signal hoist.

Some flags have pretty obvious meanings, e.g. the Speed flag. Other flags, such as Corpen, can have many meanings depending on how it is used, where in the signal hoist it is found, what type of formation is currently in effect, etc. Some non-intuitive examples are given below:

  • In its simplest usage, Corpen means course. The signal Mike Corpen Two Three Zero breaks as My course is two three zero degrees True. But Corpen Zero Niner Zero signals that a column of ships will turn in succession (as each reaches the point where the lead ship turned) to true course 090 (think of a column movement when marching, if that helps). Yet if you're in a different formation (not in a column), the meaning of the exact same signal is different. A carrier will signal Fox Corpen XXX, in which XXX degrees True is the planned course for flight operations (but don't you believe it – the carrier always lies, and will roar off in search of the flight deck wind it needs without necessarily telling you in advance, and woe betide if you find yourself in front of the birdfarm!).
  • Similarly, Turn Starboard Niner breaks as a simultaneous turn by all ships, ninety degrees to starboard, yet Turn Starboard Zero Niner Zero breaks as a simultaneous turn to course zero nine zero degrees true, pretty much regardless what formation you are in.
  • Designation (spoken Desig) is typically used to ascribe a name to something; for example, Echo X-ray Three Tack Three Desig Miller Time breaks as, Upon execution, commence exercise named Miller Time.
  • Preparatory (called Prep) is used inport when getting ready for morning or evening colors. At the dip: 15 minutes prior. Closed up: 5 minutes prior. Hauled down: execute colors.
  • Tack is not a flag at all, but a six-foot length of line with a snap hook on one end and a loop on the other (signal flags have the same snap and loop arrangement to permit quick attachment and detachment of a flag from a halyard). Tack is used to take up a signal flag-sized space in a hoist of flags. It separates two signals in one hoist, or it can represent a dash.

Signals from a ship to small craft can be made using the USN / NATO numeral eight flag, with modifiers as needed.

  • Eight (flown alone) – Steer straight away from the ship.
  • Eight flown with Port – Alter course to port. When the hoist is hauled down, cease turn and steady on course.
  • Eight flown with Starboard – Alter course to starboard. When the hoist is hauled down, cease turning and steady on course.
  • Eight flown with Screen – Steer straight toward the ship.

All this wonderful complexity exists for most of the non-numerical flags, thereby leading to the need for three-inch thick binders.

A ship when underway will usually display its international radio callsign in signal flags at all times.

There are international meanings for many of the alphabetic flags; these meanings may differ from standard USN usage. In these cases, both meanings are shown in the table below.



NATO meaning

international meaning
nautical signal flag Alfa Alfa I have a diver down; keep well clear at slow speed. With three numerals, radius within which divers are working. I have a diver down; keep well clear at slow speed. With three numerals, azimuth or bearing.
nautical signal flag Bravo Bravo I am taking in, discharging, or carrying dangerous cargo. NATO: during gunnery practice, flies on engaged side
nautical signal flag Charlie Charlie "Yes" or "Affirmative." With three numerals, course in degrees magnetic.
nautical signal flag Delta Delta I am having difficulty maneuvering; keep clear. With 2, 4, or 6 numerals, the date.
nautical signal flag Echo Echo I am altering course to starboard.
nautical signal flag Foxtrot Foxtrot I am disabled; communicate with me. NATO: on aircraft carrier, conducting Flight Operations.
nautical signal flag Golf Golf I require a pilot. When flown by a fishing vessel: "I am hauling nets." With 4 or 5 numerals, longitude (last two numerals indicate minutes). NATO: guide of formation.
nautical signal flag Hotel Hotel I have a pilot onboard
nautical signal flag India India Inport (flown by both vessels on engaged side): I am coming alongside. At the dip: preparing. Closed up: ready. Hauled down: first line over. I am altering course to port.
nautical signal flag Juliet Juliet Inport, your radio callsign followed by JULIETT indicates that ship has a semaphore message for you. Addition of DESIG indicates priority message. "I am on fire and have dangerous cargo; keep clear," or "I am leaking dangerous cargo."
nautical signal flag Kilo Kilo I wish to communicate with you. With numeral 1, via semaphore; numeral 2, via megaphone; numeral 3, via flashing light; numeral 4, via sound signals.
nautical signal flag Lima Lima Inport: This ship is under quarantine. Underway: You should stop your vessel immediately. With 4 numerals, latitude; first 2 numerals signify degrees, second two numerals indicate minutes.
nautical signal flag Mike Mike Inport: Medical guard duty. Underway: My vessel is stopped; making no way. My vessel is stopped; making no way.
nautical signal flag November November "No," or "Negative."
nautical signal flag Oscar Oscar Man overboard.
nautical signal flag Papa Papa Inport: All personnel return to ship; proceeding to sea. Underway, when used by a fishing vessel: "My nets have come fast upon an obstruction."
nautical signal flag Quebec Quebec Boat recall; all boats return to ship. With one or more numerals, number of boat which is to return. Ship meets health regulations; request clearance into port.
nautical signal flag Romeo Romeo Inport: Ready duty ship. At Sea (flown on engaged side) at the dip: Preparing to replenish. Closed up: ready to receive you, or commencing approach. Hauled down (both ships): messenger line in hand. The way is off my ship. With one or more numerals, distance in nautical miles.
nautical signal flag Sierra Sierra Conducting flag hoist drill. I am operating astern propulsion. With one or more numerals, speed in knots.
nautical signal flag Tango Tango Do not pass ahead of me. Keep clear; engaged in trawling. With 4 numerals, local time.
nautical signal flag Uniform Uniform You are running into danger.
nautical signal flag Victor Victor I require assistance. With one or more numerals, speed in kilometers per hour.
nautical signal flag Whiskey Whiskey I require medical assistance.
nautical signal flag X-ray X-ray Stop carrying out your intentions and watch for my signals.
nautical signal flag Yankee Yankee This ship has visual communications duty. I am dragging anchor.
nautical signal flag Zulu Zulu I require a tug. With one or more numerals, Zulu (GMT) time. When flown by fishing vessels: "I am shooting nets."
nautical signal flag Code Code / Answer Following signal is from the International Code of Signals. Message is understood. Also, numeric decimal point.
nautical signal flag first
substitute First Substitute Absence of flag officer or unit commander (inport only) Substitute for first flag in this hoist.
nautical signal flag second
substitute Second Substitute Absence of Chief of Staff (inport only) Substitute for second flag of this hoist.
nautical signal flag third
substitute Third Substitute Absence of Commanding Officer (inport only) Substitute for third flag of this hoist.
nautical signal flag fourth
substitute Fourth Substitute Absence of civil or military official whose flag is flying on this ship (inport only) Substitute for fourth flag of this hoist.
nautical signal flag 0 Zero Numeral zero. Also, at the dip: My engines are shut down. None
nautical signal flag 1 One Numeral one. None
nautical signal flag 2 Two Numeral two. None
nautical signal flag 3 Three Numeral three. None
nautical signal flag 4 Four Numeral four. None
nautical signal flag 5 Five Numeral five. Underway, flown alone: Breakdown. None
nautical signal flag 6 Six Numeral six. None
nautical signal flag 7 Seven Numeral seven. None
nautical signal flag 8 Eight Numeral eight. None
nautical signal flag 9 Nine Numeral nine. None
nautical signal flag P0 P0 Pennant Zero Numeral zero
nautical signal flag P1 P1 Pennant One Numeral one
nautical signal flag P2 P2 Pennant Two Numeral two
nautical signal flag P3 P3 Pennant Three Numeral three
nautical signal flag P4 P4 Pennant Four Numeral four
nautical signal flag P5 P5 Pennant Five Numeral five
nautical signal flag P6 P6 Pennant Six Numeral six
nautical signal flag P7 P7 Pennant Seven Numeral seven
nautical signal flag P8 P8 Pennant Eight Numeral eight
nautical signal flag P9 P9 Pennant Nine Numeral nine
nautical signal flag CORP CORP Corpen
nautical signal flag NEGAT NEGAT Negative
nautical signal flag DESIG DESIG Designate
nautical signal flag Turn Turn
nautical signal flag INT INT Interrogative
nautical signal flag EMERG EMERG Emergency
nautical signal flag Speed Speed
nautical signal flag Station Station
nautical signal flag
Starboard Starboard
nautical signal flag Port Port
nautical signal flag FORM FORM Formation
nautical signal flag PREP PREP Preparative; inport: morning/evening colors (flown on SOPA)
nautical signal flag FLOT FLOT Flotilla
nautical signal flag SQUAD SQUAD Squadron
nautical signal flag SUBDIV SUBDIV Subdivision
nautical signal flag DIV DIV Division
nautical signal flag Screen Screen
(no flag – just a 6-foot length of line) Tack Used to separate signals in the same hoist.

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