SeaMemo
Nautical flags: the 26 maritime signal flags and what they mean
Nautical flags are the international signal code used at sea: 26 signal flags stand for the letters A to Z. Flown alone, almost every one has a fixed meaning, such as A: diver down, O: man overboard and V: I require assistance. N over C is a distress signal. This guide shows every flag, the signals that matter to sailors and how to read them.
All 26 flags from A to Z
The meanings are the single letter signals from the International Code of Signals. The word next to each letter is the phonetic word you use to spell that letter over the radio.
| Flag | Letter | Meaning when flown alone |
|---|---|---|
| AAlfa | I have a diver down; keep well clear at slow speed. | |
| BBravo | I am taking in, discharging or carrying dangerous goods. | |
| CCharlie | Yes. | |
| DDelta | Keep clear of me; I am maneuvering with difficulty. | |
| EEcho | I am altering my course to starboard. | |
| FFoxtrot | I am disabled; communicate with me. | |
| GGolf | I require a pilot. From fishing vessels on the grounds: I am hauling nets. | |
| HHotel | I have a pilot on board. | |
| IIndia | I am altering my course to port. | |
| JJuliett | I am on fire and have dangerous cargo on board; keep well clear of me. Or: I am leaking dangerous cargo. | |
| KKilo | I wish to communicate with you. | |
| LLima | You should stop your vessel instantly. | |
| MMike | My vessel is stopped and making no way through the water. | |
| NNovember | No. | |
| OOscar | Man overboard. | |
| PPapa | In harbor: all persons should report on board, the vessel is about to sail. From fishing vessels at sea: my nets have fouled an obstruction. | |
| QQuebec | My vessel is healthy and I request free pratique. | |
| RRomeo | No meaning as a single flag. | |
| SSierra | I am operating astern propulsion. | |
| TTango | Keep clear of me; I am engaged in pair trawling. | |
| UUniform | You are running into danger. | |
| VVictor | I require assistance. | |
| WWhiskey | I require medical assistance. | |
| XXray | Stop carrying out your intentions and watch for my signals. | |
| YYankee | I am dragging my anchor. | |
| ZZulu | I require a tug. From fishing vessels on the grounds: I am shooting nets. |
A complete set has 40 flags: the 26 letters, 10 numeral pennants, 3 substitutes for repeating a flag, and the answering pennant.
The flags sailors should know
You don't need all 26 by heart to be safer on the water. These are the ones to recognize:
- A, the diver down flag: Keep clear and slow down. When a diving vessel is too small to show the usual shapes, COLREGs Rule 27 calls for a rigid replica of flag A at least 1 meter high. In the US and some other countries you'll also see a red dive flag with a white diagonal stripe.
- O, man overboard: It's often attached to the man overboard pole.
- V and W: V means I require assistance, W means I require medical assistance.
- U, you are running into danger: If someone shows you this, check your position and course right away.
- Y, I am dragging my anchor: How to spot this early is in the guide how to anchor a boat.
- P, the Blue Peter: In harbor it calls everyone back on board because the vessel is about to sail.
- Q, the yellow flag: My vessel is healthy and I request free pratique. Each country decides if and when you have to fly it on arrival, so check before you get there.
How to read a flag signal
The code has three kinds of signals: single letters for very urgent or common messages, two letter signals for the general section and three letter signals starting with M for the medical section. Flags are hoisted one above the other on a line and read from the top down. Some examples:
| Signal | Meaning |
|---|---|
| NC | I am in distress and require immediate assistance. |
| CB | I require immediate assistance. |
| AC | I am abandoning my vessel. |
| AN | I need a doctor. |
| DX | I am sinking. |
| QU | Anchoring is prohibited. |
The receiver hoists the answering pennant halfway on seeing a signal and all the way up once it is understood. In a real emergency use everything else on board first, like the radio and flares. For most conversations at sea, the radio long ago replaced flags.
Flags and day shapes show what a vessel is doing. Who you therefore have to give way to, such as a fishing boat or a vessel restricted in her ability to manoeuvre, is in our guide to COLREGs right of way.
Your boat name in signal flags
This works with Latin letters; accented letters become the base letter. It's a fun idea for crew shirts or a trip photo, but in practice people rarely spell out whole words with flags.
How to memorize the flags by pattern
The fastest way to learn the flags is in groups. The pattern usually gives the group away:
- One color: Q is all yellow, B is red with a swallowtail.
- Swallowtail: only A and B.
- Split vertically: A, H, K, T and the stripes of G.
- Split horizontally: C, D, E, J.
- Square in the middle: P, S, W.
- Four fields or checkerboard: L, U, N.
- Crosses: M and V diagonal, R and X upright.
- A shape of their own: F with a diamond, I with a disc, O and Y split diagonally, Z with four triangles.
Signal flags or semaphore?
The two get mixed up all the time. With the flag alphabet each colored flag stands for one letter. With semaphore one person holds two identical flags and the position of the arms gives the letter.
Dressing overall: signal flags for celebration
The place you'll see signal flags most often is on a dressed ship: a line of flags runs from the bow over the masts to the stern. It belongs to celebrations and harbor festivals. The order is chosen so that no message is spelled out, and national flags don't belong in the line.
Courtesy flag: the one you'll actually need
On a charter boat you're more likely to fly a flag that isn't part of the alphabet at all: the courtesy flag. It's a small national flag of the country you're visiting, flown by custom on the starboard side of the mast. If you bring your own, put it on your sailing packing list. Whether there's one on board is something to settle at the charter boat handover at the latest.
Eyes on the flags, trip in the logbook
SeaMemo doesn't replace signaling equipment. It's your logbook: the app records your route and sea miles by GPS, and you share lists and memories with your crew. If you're practicing flags, you'll probably want the essential sailing knots and channel markers and buoys too.
Sources
- International Code of Signals, Pub. 102 (PDF): meanings, the set of 40 flags, examples, distress signals
- COLREGs Rule 27: rigid flag A for diving operations
- Wikipedia: International maritime signal flags: overview
- Wikipedia: Flag semaphore: difference from signal flags
- Wikipedia: Dressing overall: order of the flags
- Wikipedia: Maritime flag: courtesy flag
- Wikipedia: Gastlandflagge (German): custom of flying it to starboard
- Wikipedia: Diver down flag: red dive flag
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Frequently asked questions
How many nautical flags are there?
There are 26 flags for the letters A to Z. A complete signal set has 40, adding 10 numeral pennants, 3 substitutes and the answering pennant.
Which flag means man overboard?
Flag O, split diagonally into red and yellow. It's often attached to the man overboard pole on boats.
What does flag A mean?
I have a diver down; keep well clear at slow speed. The white and blue swallowtail flag is also called the diver down flag.
Which flags mean distress?
The signal NC, N over C, is an internationally recognized distress signal. V means I require assistance, W means I require medical assistance. In a real emergency use the radio and other distress signals first.
What's the difference between signal flags and semaphore?
With signal flags each flag shows one letter. With semaphore the arm position of a person holding two identical flags shows the letter.