10 Common Nautical Signal Flags and Their Meanings


Nautical signal flags have been an essential tool in maritime communication for centuries. These flags are a symbolic and visual way to communicate among ships, and they serve as a universal language, easily understood no matter what language a crew may speak. There are ten common signal flags used that each have their own specific meaning. It is crucial for sailors to understand the different signals to ensure safe navigation on the seas. In this article, we will explore the history of nautical signal flags, the development of international code flags, and the meanings of the ten most commonly-used nautical signal flags, including Alpha, Bravo, Charlie, Delta, Echo, Foxtrot, Golf, Hotel, November, and Oscar.

Explanation of Nautical Signal Flags

Nautical signal flags are used as a means of communication between ships at sea. Each flag represents a different letter or phrase with its own unique meaning. Together, these flags form a code that can be used to convey important messages visually. Understanding the meanings of nautical signal flags is essential for anyone involved in maritime activities, including boaters, sailors, and Coast Guard personnel.

Nautical signal flags are typically made of lightweight and durable materials, such as nylon or polyester, and come in a range of sizes. They are typically rectangular in shape and feature bold colors and patterns to make them easy to differentiate at a distance.

To ensure effective communication, nautical signal flags are arranged in a particular order on flagpoles. This order is different depending on the type of message being conveyed. For example, the International Code of Signals specifies how to arrange flags to spell out specific words or phrases.

In addition to visual communication through nautical signal flags, there is also a common nautical phonetic alphabet that is used to communicate letters and numbers over the radio when speaking may be difficult.

Nautical signal flags have a rich history and continue to play an important role in maritime communication today. To learn more about the history and meaning of nautical signal flags, check out our article on nautical signal flags history and meaning. For information on using nautical signal flags while boating, see our article on nautical signal flags for boating. While many of these flags may no longer be used for their original purposes, they remain an important part of maritime culture and tradition.

History of Nautical Signal Flags

Nautical signal flags have a long and rich history that dates back to ancient maritime cultures. The use of flag signals was prevalent among sailors, merchants, and pirates even in ancient times. In the 19th century, the development of international code flags, which consists of 26 flags representing different letters, allowed for a standardized system of communication between ships. The use of nautical signal flags continued throughout the 20th century, but technology advancements reduced its use to a backup system. However, nautical signal flags are still made and used today on various occasions, such as international yacht races and military exercises. To learn more about how nautical signal flags are made and used today, check out our guide on nautical signal flags made and used today.

Origins of Signal Flags

The origins of signal flags date back to ancient maritime history, when sailors would communicate with each other using primitive methods such as shouting and waving. As maritime technology advanced, so did the forms of communication. One of the earliest recorded instances of signal flags being used was during the ancient Greek and Roman eras, where semaphore towers were set up along the coast to relay messages.

During the Middle Ages, signal flags were used by pirates and privateers to communicate with one another while avoiding detection by other ships. These early forms of communication were often crude and simple, consisting of flags with basic designs and colors. However, over time, more complex and sophisticated forms of signal flags were developed.

In the 17th and 18th centuries, signal flags became an integral part of naval operations. Ships would use signal flags to communicate with one another, often in crowded harbors or during times of battle. The use of signal flags allowed for faster and more efficient communication, allowing ships to coordinate their movements and actions with one another.

One of the first recorded instances of standardized signal flags being used was by the British Navy in the 18th century. The British developed a system of colored signal flags that could be hoisted up in specific combinations to communicate different messages. This system was later adopted by other navies around the world.

In the 1850s, the International Code of Signals was established, which standardized the use of signal flags among different nations. This system uses a set of flags and codes that are recognized by all participating countries, allowing for universal communication between ships of different nationalities.

The origins of signal flags demonstrate the importance of communication in maritime history and the evolution of technology. From simple forms of communication to more complex and sophisticated systems, signal flags have played a key role in the development of modern navigation.

Development of International Code Flags

The development of International Code Flags dates back to the late 19th century. In 1857, the British Board of Trade introduced a International Code of Signals for use by British ships. However, it was in 1901, when the International Radiotelegraphic Conference was held in Berlin, that the first official International Code of Signals was established. The code is composed of 26 square flags, representing letters of the alphabet, plus 10 numerical pennants and 3 substitutes.

The International Code of Signals is designed to enable ships from different countries to communicate with each other, regardless of language barriers. The flags have specific meanings, and when flown together, they can convey messages to other ships, including distress signals.

Over the years, the Code has been updated and modified as technology and international communication have evolved. For example, in the 1960s it was revised to include signals for use with radio-telephony and radiotelegraphy. But the original system of using brightly colored flags to communicate over distances still remains the backbone of the International Code of Signals.

One of the most important changes that has been made to the Code of Signals in recent years has been the introduction of digital technologies to the system. Ships can now send and receive messages using digital formats, such as email or fax. This has been a key development for the safety of shipping, making it easier for ships to communicate with each other and with coastal stations.

The development of International Code Flags has been critical to the safety of shipping, allowing crews to communicate quickly and effectively with other vessels, regardless of language barriers. While technologies such as email and digital messaging have become commonplace, the original system of using brightly colored flags to communicate over distances still remains an integral part of the International Code of Signals.

10 Common Nautical Signal Flags

Nautical signal flags have been used for communication among ships for centuries. There are a wide variety of signal flags, but 10 common nautical signal flags are Alpha, Bravo, Charlie, Delta, Echo, Foxtrot, Golf, Hotel, November, and Oscar. Each of these flags has a specific meaning and can convey different messages depending on how they are arranged. Alpha, for example, means “divert your course to port,” while Bravo means “dangerous cargo.” Charlie is used to indicate “yes” or “affirmative,” whereas Delta means “keep clear of me.” Echo is used to convey the message “I am altering my course to starboard,” while Foxtrot means “I am disabled, communicate with me.” Golf means “I require a pilot,” while Hotel means “I have a pilot on board.” November means “no” or “negative,” and Oscar is used to indicate “man overboard.” Knowing the meanings of these 10 common signal flags can help ensure safe navigation and clear communication among ships.


The nautical signal flag Alpha is one of the most commonly used flags in the International Code of Signals. It is a yellow and white flag that features a solid yellow triangle on a white background. This flag is used to indicate that a vessel has personnel on board who are either in the process of diving or are preparing to dive.

The meaning of Alpha Flag

The Alpha flag is used as an alerting signal flag. It signals other boats in the vicinity to keep a safe distance from the vessel exhibiting it. This is because diving operations can be dangerous and require the full attention of the crew on board. The Alpha flag is raised and flown from the port yardarm of a vessel when it is stationary and diving operations are in progress, or about to commence.

When to use Alpha Flag

The Alpha flag must be flown when divers are operating within 100 metres of a vessel or within a channel or fairway. The presence of a diver in the water requires other vessels in the area to keep a safe distance or reduce their speed so as not to disturb the diving operations. If any vessel is observed to be flying an Alpha flag, all other boats must reduce their speed to a minimum and keep a safe distance.


The Alpha flag is a crucial part of the International Code of Signals, and its meaning must be thoroughly understood by all seafarers. As diving operations can be dangerous, the proper use of this flag can help to ensure the safety of divers and their support crew, as well as other vessels in the area.


The signal flag is one of the most commonly used flags in nautical communication. It features a blue and white checkered pattern and is used to indicate that a vessel is loading, unloading, or carrying dangerous cargo. When flown alone, it indicates that the ship has the intention of carrying out these activities.

This flag is part of the International Code of Signals and plays a crucial role in ensuring safe and efficient navigation. Having the ability to communicate the presence of hazardous cargo can prevent accidents and allow other vessels to take the necessary precautions.

Interestingly, the word ‘bravo’ comes from the Spanish language and was originally used in bullfighting. The term was used to commend the performance of a skilled matador. This eventually evolved into its current usage as an expression of acclaim or approval.

In addition to its use in nautical communication, the Bravo flag is also used in aviation to indicate a similar warning. When used in this context, it signals the presence of dangerous materials such as explosives or flammable liquids.

It’s important to note that the Bravo flag should only be used by vessels or aircrafts that are specifically designated to transport dangerous goods. If seen flown indiscriminately, it could cause confusion or unnecessary alarm. The use of the Bravo flag is an essential aspect of safe navigation in both nautical and aviation contexts.


Charlie is one of the ten most common nautical signal flags used to communicate between ships. It is also a letter in the International Code of Signals (ICS), where it denotes “Yes” or “Affirmative.” But when used alone as a flag, Charlie has a different meaning.

Charlie means “I am carrying dangerous cargo.” This could be anything that poses a threat to health, safety, or the environment, such as explosives, petrol, chemicals, or radioactive materials. The purpose of the Charlie flag is to alert other ships, ports, and authorities of the potential danger, so they can take appropriate measures to avoid accidents, leaks, spills, or contamination.

The Charlie flag is rectangular and divided diagonally from the top hoist to bottom fly into black and yellow triangles. The black triangle is on top and the yellow triangle is on the bottom. The flag is easy to recognize from a distance, especially if it is flown together with other relevant flags or signals, such as the X-Ray flag, which means “Stop carrying out your intentions and watch for my signals.”

Some common phrases that can accompany the Charlie flag are:

– “I am carrying dangerous cargo of class… (explosives, flammable liquids, toxic substances, etc.)”
– “I am a nuclear-powered vessel.”
– “I am a submarine.”
– “I am an aircraft carrier.”

It is important to note that the Charlie flag is not the only way to communicate about dangerous cargo. Ships are also required by law to carry documents such as the International Maritime Dangerous Goods (IMDG) Code, which provides information about the type, quantity, and handling of hazardous goods. However, using the Charlie flag in conjunction with these documents can increase the visibility and urgency of the message.

The Charlie flag is a crucial tool for maritime safety, helping to prevent accidents and protect human lives and the environment. If you see this flag flying on a ship, it is best to give it plenty of space and avoid any risky maneuvers.


Delta is a nautical signal flag that holds great importance when it comes to communication at sea. It is a yellow triangular flag with a blue triangle at the center. Delta is also known as the “Code Flag D”, and it holds a special message for ships and boats to heed during their journey.

This flag signifies the urgent need for a vessel to communicate with a pilot or a ship’s agent or to request a pilot at the next port. It can also be used to represent “Keep Clear”, which means that a vessel is engaged in underwater operations and other boats must keep a safe distance from it. Delta can also be used when a vessel is carrying dangerous goods or explosives.

The meaning of Delta is crucial in ensuring the safety of all ships and boats at sea. It can help prevent accidents and collisions, and it is important for all sailors to understand the message that it conveys. Ignoring a Delta flag can result in grave consequences, both for the crew of the vessel carrying the flag and for other ships and boats in the vicinity.

It is also worth noting that while Delta is used as a signal flag in the nautical world, it is also used as a symbol in various other fields. In aviation, for example, it is used to represent the letter “D” in the NATO phonetic alphabet. In mathematics, it is used to represent the change in a function, and in science, it is used to represent the fourth letter of the Greek alphabet.

The Delta nautical signal flag holds great meaning in the world of sailing. Its message is vital for ensuring the safety of all vessels at sea, and it should never be ignored or taken lightly. Understanding the message that Delta conveys can help prevent accidents and collisions and keep everyone on board a ship or boat safe.


Echo is the fifth signal flag in the International Code of Signals, denoted by a white flag with a blue square in the center. When hoisted, the “Echo” flag indicates the vessel is altering course to starboard (right) . This signal flag is often used when two ships are close to each other and there is a potential risk of collision. Echo flag can be used alone, in pair or with additional signal flags, depending on the situation.

Echo flag has a long and interesting history. It was originally devised by the British Navy and was first introduced in 1855 under the name “Economy”. The original purpose of the flag was to save time and effort by creating a single signal flag to denote a specific maneuver rather than signaling the entire maneuver using multiple flags.

Using the “Echo” flag can be crucial in avoiding collisions at sea. As ships approach each other, there is often confusion about which vessel has the right of way or which direction they intend to navigate. By hoisting an Echo flag, a vessel can alert other ships in the vicinity of its starboard course change so that they can adjust their own course accordingly. It is vital that the communication between different vessels is clear and concise in order to avoid accidents and potential maritime disasters.

In addition to its practical use, the Echo flag also has a symbolic meaning amongst seafarers. It signifies an appreciation for teamwork and communication necessary for safe navigation at sea. Without clear communication and coordinated efforts by the crew members, a vessel is more susceptible to accidents and becoming lost.

All in all, the “Echo” flag represents an important piece of nautical history and serves as a critical tool for safe marine navigation. Its use should be thoroughly understood by all seafarers to help avoid mishaps on the high seas.


Foxtrot is one of the 10 common nautical signal flags used to communicate messages between vessels. Here is what you need to know about this signal flag:

Flag Signal Meaning
F FOXTROT I am disabled; communicate with me.

The Foxtrot signal flag indicates that a vessel is experiencing some sort of malfunction or damage and requires communication with other vessels. This flag is typically flown alongside the international signal for distress, which is a square flag with a diagonal stripe.

In this situation, the crew aboard the disabled vessel may need assistance or simply want to communicate their situation with other vessels in the area. The Foxtrot flag is a way to alert other vessels of their situation and request coordination or help if necessary.

It is important for all vessels to understand the meaning of the Foxtrot signal flag and respond accordingly. If a vessel recognizes the flag and can provide assistance, they should contact the disabled vessel and offer their support. Failure to respond to a disabled vessel could lead to dangerous situations, so it is always important to be on the lookout for signal flags and be prepared to respond appropriately.


The signal flag for “Golf” is a white square with a blue circle in the center. When hoisted, it signals to other vessels the message: “I require a pilot.” This signal is used by a ship’s captain when they need expert navigational assistance in unfamiliar waters or difficult conditions. A pilot is a highly skilled navigator who has extensive knowledge of a specific area’s local waters and can assist the captain with safe navigation in the area. It is common for ocean-going vessels to take on a pilot as they approach a harbor.

Interestingly, the origin of the word “pilot” comes from the Greek word “peleia”, meaning ballast. A pilot would serve as an additional ballast on a ship. Over time, the role of a pilot has evolved to include providing expert guidance and advice to captains as they navigate through dangerous waters.

It’s important to note that pilots are not part of a ship’s crew. Instead, they are licensed professionals who work for pilot organizations or local authorities. When a ship requires a pilot, they typically contact a pilot organization to request the service. The organization then arranges for a pilot to meet the vessel as it approaches the harbor.

The use of pilot boats is common in many ports. These boats are specifically designed to transport pilots to and from ships. They are typically fast and maneuverable, allowing pilots to board and disembark from vessels safely and quickly.

The “Golf” signal flag is an important way for ship captains to communicate with pilots and navigate through unfamiliar waters safely. By working together, captains and pilots can ensure the safety and success of their voyage.


The nautical signal flag for Hotel is a white and blue square divided diagonally with the blue portion on top. This flag is used to signify that a ship is seeking a pilot. A “pilot” is a professional navigator who provides advice and guidance to ships in navigating dangerous or congested waters. It’s important to note that a pilot’s presence doesn’t necessarily mean that a ship’s captain is inexperienced, but rather the pilot is there to assist with local waterways.

The origin of the “hotel” name for this flag is uncertain. Some theories suggest that it comes from the French word “hôtel,” meaning “hostel,” which could imply the need for a safe harbor. Other theories suggest that it may come from the English word “hotel,” which in maritime terms could refer to a dock or port facility. Nonetheless, it remains a mystery.

Aside from being a signal flag for pilots, Hotel flag can be used as part of a set of international code flags to send messages related to navigation and communication. Here are some examples:

Code Flag Combination Meaning
Hotel – Lima – Lima “I require a pilot”
Hotel – Oscar “I have a pilot on board”
Hotel – India “I am altering my course to port”

It’s essential that sailors understand the meanings of nautical signal flags to ensure safe and effective communication on the water. Knowing how to request a pilot or indicate a change in course can prevent accidents and minimize risks.


November is a nautical signal flag with a yellow and black diagonal stripe. It is an important flag used to convey a specific message to other boats. In general, November means “no,” “negative,” “stop,” or “I am not able to comply with your request.”

This flag is also known as the “Negative” flag and shouldn’t be ignored by boats around. When one or many boats use the November flag, it means that there is an obstacle or issue that is preventing them from complying with your request. This could be anything from a mechanical malfunction, difficult weather conditions, or even simply that the boat is unable to change course safely.

Boaters use the November flag in a number of different situations:

  • Medical Emergency: If a person onboard falls sick or is injured seriously, and the boat needs an urgent return or seeks immediate help from a nearby vessel, the captain raises the November flag.
  • Breach Of Safety: In case of any leak or fire risk, the captain uses the November flag to signal that it is not safe to approach that boat.
  • Loss of Control: If the captain has no control over the boat’s direction due to strong currents or other issues, he raises the Negative flag to signal other vessels that he cannot control his vessel.
  • Message Not Understood: The November flag is also used to signal that the message was not understood or was misinterpreted. This may be due to language barriers or radio interference. It’s important to pay attention to the November flag in this situation so that you can clarify your message effectively.


The nautical signal flag Oscar is used to signify the phrase “Man Overboard.” It’s a simple but crucial piece of equipment for any vessel’s crew to have on hand.

If a crew member falls overboard, the Oscar signal flag is raised to alert the rest of the crew. Depending on the situation, the crew can then begin search and rescue operations to recover the missing crew member.

While the Oscar signal flag can be used on any vessel, it’s particularly useful for larger ships with many crew members. In these situations, spotting a crew member who has fallen overboard can be difficult without assistance from the rest of the crew.

Interestingly, the origin of the phrase “Man Overboard” dates back centuries. In the days of sailing ships, crew members who fell overboard were considered a lost cause. However, as more advanced ships and equipment were developed, it became possible to rescue crew members who had fallen overboard. Today, the Oscar signal flag and other safety equipment are critical for ensuring crew safety on any vessel.

It’s important for all crew members to understand the meanings of nautical signal flags like Oscar. By learning and practicing their use, crew members can help keep each other safe and react quickly in emergency situations.


In conclusion, understanding the meanings of nautical signal flags is essential for safe and effective communication at sea. Knowing the meanings of these flags can help sailors and boaters avoid potential dangers, signal for assistance, and communicate effectively with other vessels.

By exploring the history and development of nautical signal flags, we can appreciate the significance of their role in maritime culture and safety. The ten most common signal flags, Alpha, Bravo, Charlie, Delta, Echo, Foxtrot, Golf, Hotel, November, and Oscar, all have unique meanings that are easily identifiable.

Whether you are a seasoned sailor or a novice boater, taking the time to learn about these flags can improve your communication skills and help you navigate the waters with confidence. So, next time you’re out at sea, keep an eye out for these common nautical signal flags and decipher their meanings. Stay safe and enjoy the adventure!

Frequently Asked Questions

What are nautical signal flags used for?

Nautical signal flags are used to communicate important messages between ships at sea.

Are nautical signal flags still relevant in today’s digital age?

Yes, nautical signal flags are still relevant as they provide a universal system of communication that can be recognized by all ships, regardless of their country of origin.

How many nautical signal flags are there?

There are a total of 26 nautical signal flags, one for each letter of the alphabet.

What is the history behind nautical signal flags?

Nautical signal flags have been used for centuries by ships at sea to communicate with each other when they are out of earshot.

Can nautical signal flags be used to send secret messages?

Yes, nautical signal flags can be used to send secret messages, as long as both the sender and recipient understand the code being used.

What are some other uses for nautical signal flags?

Nautical signal flags can also be used in various maritime ceremonies, such as yacht racing and ship christenings.

What does the “Delta” signal flag mean?

The “Delta” signal flag is used to indicate “keep clear” or “I am maneuvering with difficulty, communicate with me.”

What does the “Foxtrot” signal flag mean?

The “Foxtrot” signal flag is used to indicate “I am disabled, communicate with me.”

What does the “Hotel” signal flag mean?

The “Hotel” signal flag is used to indicate “I have a pilot on board.”

What does the “Oscar” signal flag mean?

The “Oscar” signal flag is used to indicate “man overboard.”


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