Racing Signals: Sailing Flag Meanings

Racing Signals: Sailing Flag Meanings | Life of Sailing

Last Updated by

Gabriel Hannon

August 30, 2022

Where other competitions have umpires and referees right next to the players, sailing race committees have to rely on flags to communicate with sailors.

In this article, we are going to explain the meanings of all the flags used at regattas to communicate with sailors. The flags can give information about starting procedures, course information, and on-the-water judging, so a basic understanding is a crucial part of general seamanship.

While nautical flags all have defined meanings in a historical context, they have very specific meanings in the context of racing competition. For instance, in the general nautical world, the Z-flag means that you are in distress and are in need of a tow or relief from a tug boat. At a regatta, the race committee may fly the Z-flag to indicate an additional penalty for any boat that has crossed the line early. Moreover, even though there are certain flags that have well-defined roles, race committees may stipulate additional meanings or introduce new flags via an announcement in the sailing instructions for the event, so we will cover some of these more common changes as well. We will break down the meanings into the various categories of usage.

A secret that I have learned over many years of regattas at every level from proverbial ‘beer-can’ races to national championships is that, as well as both you and the race committee can recite the racing flag rules on land, someone is always going to make a mistake or misunderstand these symbols. That is why I will be going through the official flag meanings and rules from the Racing Rules of Sailing for 2021-2024 to clarify any questions that you might have when the race committee flies a flag that hasn’t been seen since we used Clipper Ships to cross the oceans. Hopefully this article will help break down all the most common signals so that when your friend turns to you and asks ‘is that the flag that tells us it's time to go in,’ you’ll be able to help out!


Table of contents

Flags at the Start

The start of a race is often the most confusing part of a regatta and is where the most flags must be used. We will be going over the rules for the flags at a basic 5-minute start. These can be modified for 3-minute dinghy starts, 5-minute match race starts, 6-minute Olympic starts, or 10-minute big boat starts, but the same logic applies.


A few flags are crucial to set everything up on the starting line prior to the starting sequence.


To begin, the race committee must have an Orange Flag visibly displayed, as this demarks the exact location on the boat from which the line is called. If there is a pin boat, they will often fly an Orange Flag as well, but if it is just a buoy, then the buoy serves as the other end of the line.


Next, the RC will additionally fly the L Flag if they are ready for competitors to check-in at the beginning of the race day. This helps them confirm that everyone is sailing under the correct sail number, which is often a logistical nightmare. They will blow one horn when raising this flag. If this flag is raised at any point later in the day, it is meant to tell competitors to come by the committee boat again.


Finally, the AP Flag is a general purpose postponement flag. The race committee may raise this on land to indicate that the harbor start has been delayed or on the water to indicate that there will be a delay in the starts. While there are other flags that are used for abandonment situations, particularly the N Flag, the AP is commonly used in informal situations. Two sounds accompany the raising of the AP, and it can be said that competitors are ‘under AP’ until it is dropped, along with one sound. If it is dropped on land, competitors may immediately launch. If it is dropped on the water, the next start may begin in as little as one minute.


The final note with the AP Flag is that the race committee may indicate the end of racing for the day by flying ‘AP over A.’ Again, the AP could technically be replaced with the blue and white checkerboarded N Flag, but the two serve very similar purposes at most levels.

Starting Flags


Once the race committee is set up and everyone is ready to go sailing, the next task is to get the right fleets to the starting line for their start. At the warning signal, one loud horn that indicates that the 5-minute countdown to the start has begun, the race committee will raise some type of Class Flag that indicates which type of boat will be starting. Above we have the different class flags for the different competition rigs for the ILCA-Dinghy, formerly known as the Laser, which would be raised to indicate which rig is starting.


This is a convention even if there is only one class on the water. Sometimes this is replaced with raising the Orange Flag itself, or some other flag as laid out in the sailing instructions. Often classes have been assigned a numeral pennant, of which 1-4 are displayed above, in place of the highly specific Class Flags. Still, some flag of this nature goes up at 5-minutes and remains up until go, at which point it is dropped.


At 4-minutes, the RC will sound another horn, known as the preparatory signal, and raise some combination of the above flags.

The P Flag is always required to go up, and it is simply the ‘Prep Flag,’ which signals to the racers that they need to get serious about the race. Once the P Flag is raised, all the right-of-way rules that apply during the start switch on and racers, particularly in team and match racing, are allowed to begin tactically engaging with each other (though in team racing this would happen at minute 2 of the 3-minute start). Moreover, racers can talk with their coaches until the prep signal, and race committees may alter the course up until this moment. Afterwards, all coaching is banned and all course changes on the current leg are not allowed. This belies the fact that a 5-minute starting sequence is actually a 4-minute sequence with a warning signal at 5-minutes, but that is a purely semantic detail.

Depending on how rowdy the competitors are, the race committee may raise any combination of the I, Z, U, or Black Flags. Each of these flags deals with boats that start ‘on-course side’ (OCS), essentially a false start for sailing. If any of these flags is raised, a boat is not allowed to be anywhere within the triangle formed by the starting line and the first mark of the course after the 1-minute signal during the start. These flags essentially help the RC ensure that they can get off a clean start and ensure that they can identify any boats that are OCS at go. When they are flown, the following penalties are added beyond requiring a boat to clear itself by dipping back under the line:

  • I Flag: Conventionally referred to as the ‘one-minute rule,’ this requires that any boat over the line after a minute also has to sail around an end of the line in order to start the race fairly. This punishes a boat for being over by potentially making it a little harder to clear themselves if they are over on a large line.
  • Z Flag: Often flown in combination with the I Flag, this flag adds that any boat that is OCS will get a 20% penalty on top of their score in that race, regardless of whether they clear themselves or not. This further hurts any boat that is ‘pushing the line’ by ensuring that even if they manage to clear themselves and come back, they will still see an impact on their scoreline that is equivalent to immediately being passed by 20% of the fleet.
  • U Flag: Now we’re getting into harsh territory. When the RC is really trying to brush the fleet back off the plate, this flag immediately disqualifies a boat that is over after a minute with no course for redress. If these boats are identified, they tend to be told to stop sailing the race by a notice board at the top mark.
  • Black Flag: The black flag serves a very similar purpose to the U Flag, except it is a step harsher. It disqualifies you after a minute and even prevents you from sailing in a restart of the race or a race abandoned halfway through.

The I Flag is by far the most common flag, and is often effective at keeping boats from being over. The U Flag rule was introduced in 2013 as an option and formally codified in the Racing Rules in 2017 and is massively more popular than the Black Flag, which is considered overly punitive. In particular, when many sailors are over in a Black Flag start, such that the RC cannot determine who was over, they are forced to make unfair decisions that carry over to the restart, so the U is now almost universally used in its place. Additionally, as the U has become more popular, people tend to shy away from the Z flag, which is considered cumbersome for scorers and confusing to sailors.

In general, while these flags are supposed to be raised in conjunction with the P Flag, often the RC will only raise the most punitive of the flags, as any of them can essentially be considered as a prep flag.

As the starting sequence continues, any prep flag(s) raised must be lowered at the 1-minute signal. The class flag is then lowered at go, leading to the next category of flags: Recall Flags

Recall Flags

After the pain of raising and lowering all those start flags, the RC then has three possible jobs. If the start is clean, they shout ‘All Clear!’ and can then relax until they have to start another race or record finishes for the race in progress. Unfortunately, this is often not the case, as they likely will need to ‘recall’ certain competitors for being ‘OCS,’ i.e. false starting. They have two choices here.


If only a few, easily-identifiable boats have started early, the RC will raise the X Flag along with a single sound in what is referred to as an individual recall. This indicates to the boats on the course that there are some competitors who are currently OCS and must clear themselves. If the I Flag had been flown for the start, competitors have to round an end; if not, they can just dip back behind the starting line and restart from there.

While the X is suitable on its own to inform a boat that it has been called over, it is an oft practiced courtesy for the RC to hail an OCS boat’s sail number over a megaphone, a radio, or other transmission device. The X Flag is dropped when all OCS boats have cleared themselves or after 4 minutes from go, whichever comes first.


If more boats than can be easily identified are called over, the RC can blow two horns and fly the First Substitute Flag, indicating a general recall. In this case, the race is fully reset and the committee will initiate another entire starting sequence for that fleet. After a general recall, the RC will often, but not always employ the next level of penalty flag for the restart in an attempt to get the race off cleanly.

Sometimes, as in college sailing or as stipulated by other sailing instructions, any general recall immediately implies the I Flag for the next sequence if it had not been flown previously. As such, the RC does not necessarily have to fly the I if it is unavailable. Still, such stipulations are almost always written out explicitly for a given event and are often accompanied by a verbal announcement as a courtesy.

Still, outside some usages of the AP or N Flags to abandon or delay starts already in sequence, these are all the flags that deal with general housekeeping and the starting sequence.

While Underway

While the starting flags are by far the most complicated of the flag rules, there are still other flags to keep track of while racing. The first among these are...

Course Change Flags

Although course changes are relatively rare, race committees often pull them out when conditions change substantially during races or if there has been a problem with one of the marks.


When wind or time constraints require, the race committee may send an official to any mark of the course that no boat has yet rounded and have it raise the S Flag along with two sounds. This indicates that the fleet shall finish at that mark, cutting off the race earlier than written in the sailing instructions.


In the case of any other change to the course, such as a minor adjustment to the angle or distance of an upcoming leg, a race committee boat will go to the preceding mark and raise the C Flag along with repeated sounds.

This is sometimes accompanied by a Red Square or a Green Triangle to indicate that the mark has been moved to port or starboard respectively. Although during less formal events, you can change the positions of any marks so long as there are no competitors currently sailing on that leg of the course, it is considered poor form if at all possible to inform competitors, particularly in longer races. Sailors make decisions based on the position of the marks, and if this has been changed without them noticing, that can drastically affect the outcomes of strategic decisions, so in large competitions the C Flag is a must.


If, meanwhile, something odd has happened to a mark of the course, any official boat may fly the M Flag with repeated signals. This serves to inform the competitors that they have become a replacement for the missing mark. This is relatively uncommon, but anchors do occasionally snap on marks, so it is always good to have a support boat with the M if possible.


Finally, as mentioned before, if conditions have deteriorated to the point that a race is considered no longer possible, due to lack of wind, fear of foul weather, or some form of interference -- I’ve seen it happen because cruise ships wanted to pass through a dinghy course, and you don’t say no to them -- the race committee may abandon the race using the N Flag. Still, this flag is relatively rare as you will often see the AP in its place for convenience, as they are functionally similar.

Miscellaneous Flags

While we have covered the bulk of the flags necessary for racing at any level, there are a few more flags from across different disciplines and classes that are worth mentioning, if only to let you in on these quirky parts of the racing world! This starts with what one could reasonably call…

The Cheating Flag


Calling the O Flag the cheating flag is certainly a bit of a misnomer. The O Flag does, however, suspend Rule 42 of the Racing Rules of Sailing. Rule 42 is particularly notorious, as it bans pumping, rocking, ooching, sculling, and excessive maneuvering, all of which are methods to make your boat go substantially faster. While Rule 42 is worth an article in and of itself, the larger point is that it is meant to keep anyone from gaining an unfair advantage over their competitors.

Certain competitive classes, however, including the Olympic class 470s and Finns and many of the new foiling fleets, allow competitors to ignore Rule 42 in certain conditions, typically in heavy breezes that are referred to as ‘planing’ conditions. There are differences across the classes, but whenever it is allowed and the RC flies the O Flag, Rule 42 is switched off and competitors can ooch, pump, rock, and tack their boats all around the racecourse. This allows for a much more physical style of sailing and is a rule that many different classes and sectors of sailing are beginning to consider.


If conditions no longer meet the threshold for that class’s rules regarding suspension of Rule 42, an official boat will raise the R Flag at some point during the race. They can only do so at a mark of the course so that it is fair to all the competitors throughout the fleet. This is relatively rare, and is normally done between races, but is still a key part of the O Flag rule.

Judge and Umpire Flags

On the topic of Rule 42, there are certain fouls in sailing that can be actively enforced on the water by judges or umpires, depending on the context.

Rule 42 is enforced by judges with a Yellow Flag, which they will point at an offending boat along with a sound signal and a direct sail number hail. That boat may clear themselves from their first Yellow Flag by taking their two-turn penalty, but, unless otherwise noted in the sailing instructions, any subsequent violation can entail disqualification.

Finally, certain levels of modern match and team racing, with the addition of high-performance racing like SailGP, have full on-the-water umpires who actively follow the racing to make calls on fouls and other plays. While this is not the spot to go through the intricacies of team and match race calls, the basic gist is as follows.

In any interaction, any boat involved in the race may call in the umpires if they believe that their opponent has fouled them. If the opponent clears themselves quickly, essentially admitting fault, the umpires will not get involved. If no boats clear themselves, the umpire has to make a call on whether there has been a foul. If they determine that the maneuvers were clean, they will make one sound and fly a Green Flag, thus exonerating all boats in the interaction. If they determine there was a foul, they will fly a Red Flag with a singular sound and hail the offending boat.

Beyond that, if a boat is found to have broken a rule not related to an interaction, the umpires may come in and fly the Red Flag without being directly invited into the situation. Further, if a boat is found to be in violation of sportsmanship or refuses to take a penalty as assessed by an umpire, the umpire may fly a Black Flag, disqualifying them from the race.

While there are differences at each event and in each discipline, these general guidelines are followed in most umpired races, with specific flags used at various events, generally depending on availability.

With that, we have made it from land, through the start, a few general recalls, all the way to umpire flags! I hope this has helped you get a grasp of the various flags used across sailing. While this has not scratched the specifics of the various alterations made for kiteboards and windsurfers, nor some of the annoyances of protest flags and more, we have gone through the bulk of regularly used race committee and umpire signals.

The ‘Wear Your Life Jacket!’ Flag


Finally, we have a safety flag. At big boat regattas, the race committee may, if it chooses, fly the Y Flag at any point prior to a start to inform competitors that they must wear personal floatation devices, which is not always strictly necessary.

The Most Important Flag

While I wish I could tell you that everyone uses their flags properly and accompanies them with the proper timing and sound signals, that is far from the truth. Everyone’s flag set is slightly incomplete or out of date, and invariably there is going to be a miscommunication somewhere, where the race committee forgets to put the I Flag up but really should have; I’ve certainly done that a time or two. Still, there’s nothing quite like being on the water, so, despite the endless mutual griping between racers and their race committees, hopefully everyone comes back to shore flying the ‘Happy Flag.’

Happy sailing!

Racing Signals: Sailing Flag Meanings
Gabriel Hannon

Gabriel Hannon

I have been sailing since I was 7 years old. Since then I've been a US sailing certified instructor for over 8 years, raced at every level of one-design and college sailing in fleet, team, and match racing, and love sharing my knowledge of sailing with others!

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