Maritime flag

A maritime flag, also called a naval flag, is a flag designated for use on ships, boats, and other watercraft. Naval flags are considered important at sea and the rules and regulations for the flying of flags are strictly enforced. The flag flown is related to the country of registration: so much so that the word "flag" is often used symbolically as a metonym for "country of registration".

Types of flag

Ensigns

The ensign is the national identification of a ship and hoisted up in a national flag world-wide. They are required to be worn when entering and leaving harbour, when sailing through foreign waters, and when the ship is signalled to do so by a warship.
Ensigns are part of seafaring traditions of private and naval forces and have their origins in the era of sailing vessels. Flag dipping is done with the ensign. Ships usually wear their ensigns between the morning colours ceremony and sunset when moored or at anchor. Warships wear it at all times when underway, and when engaged in battle, wear the "battle ensign" or multiple ensigns.
Tradition dictated that if a ship lowered its ensign it was deemed to have surrendered. Masts were targets of gunfire, and the second and subsequent ensigns were worn in order to keep the ensign flying even after a mast hit.

Jacks

Jacks are flown on the bow and placed upon a jackstaff, and used when the vessel is in a port or dressed on special occasions, and not while being underway. The origin of the jack was on warships only. However, it became an additional flag for certain other vessels and is sometimes identical with the ensign on merchant ships, depending on the ship's origin.
Jacks in the Royal Navy must be run up when the first line is ashore when coming alongside.

Distinctive marks

On 16 January 1899, commissioned ships of the United States Coast and Geodetic Survey were authorized to wear their own flag to distinguish them from ships of the United States Navy, with which they shared a common ensign. Although they continued to wear the same ensign as U.S. Navy ships, ships of the Survey flew the Coast and Geodetic Survey flag as a "distinctive mark" until the newly created National Oceanic and Atmospheric Administration took over control of the Surveys ships in 1970. Since then, commissioned ships of the NOAA fleet, which also wear the same national ensign as U.S. Navy ships, have worn the flag of the National Oceanic and Atmospheric Administration as a distinctive mark.
Similarly, all ships of the United States Lighthouse Service wore the U.S. Lighthouse Service flag until the service merged into the United States Coast Guard on 1 July 1939, and ships of the United States Bureau of Fisheries wore the Bureau of Fisheries flag until the bureau was merged into the United States Fish and Wildlife Service on 30 June 1940. The Fish and Wildlife service subsequently has flown its flag as a distinctive mark on its ships.

Rank flags

The rank flag or distinguishing flag is the flag worn by a superior officer on their flagship or headquarters. The origins of this are from the era before radiotelegraphy and radiotelephony, when orders were given by flag signals. The flag denotes the ship which must be watched for signals designating orders. Such flags are also worn when leaders of the government are aboard navy ships, showing the ship to hold the headquarters of highest level of authority for the armed forces. Today, with the progress in communications, this flag indicates the obligation of the other naval vessels to pay the relevant honours according to nautical etiquette. In a group of naval ships all commanded by superior officers, only the commander of the group or the officer of the highest rank can wear his flag.

In the Royal Navy, admirals fly rectangular rank flags: an admiral of the fleet flies a Union Flag, while an admiral flies the St George's Cross. The flags of vice-admirals and rear-admirals have two and one additional red balls respectively. Commodores fly a Broad Pennant which is a short swallow-tailed pennant based on the St George's Cross, with a red ball at the canton.
In the United States Navy and the navies of some other countries, admirals fly rectangular flags with stars according to rank. Line officer flags are blue with white stars, while staff officer flags are white with blue stars.
In the United States Coast Guard, the United States Public Health Service Commissioned Corps, and the National Oceanic and Atmospheric Administration Commissioned Officer Corps, admirals fly rectangular flags with stars according to rank.
In the Hellenic Navy admirals fly blue square flags bearing a white cross with four six-point stars ; vice-admirals fly the same flag but with three stars; rear admirals two stars; and commodores one star. Captains, when commanding a flotilla or squadron, fly a burgee with the colours of Hellenic Navy Jack. When a rank flag is flown the commissioning pennant is displaced downward.
Pennants

The pennant, historically called a pennon, is a long narrow flag, conveying different meanings depending on its design and use. Examples:

A commissioning pennant, or masthead, which a warship flies from its masthead and indicates the commission of the captain of the ship. In the Royal Navy, the commissioning pennant is a small St George's Cross with a long tapering plain white fly. In the United States Navy, it is red above white, with seven white stars in the blue hoist. In the National Oceanic and Atmospheric Administration fleet, it has 13 or seven red triangles on a white background at the hoist with a long tapering blue fly. The commissioning pennant may be displaced by various rank flags, namely the flags or pennants of admirals or commodores, and the personal flags of heads of state and members of royal families. In former centuries, masthead pennants were of a length similar to that of the ships that wore them, but nowadays very long pennants tend only to be seen when a ship is paying off.
A church pennant, as used by the Royal Navy, Royal Netherlands Navy and Commonwealth Navies, is a broad pennant flown on ships and at establishments during religious services, and has the George Cross and Dutch flag incorporated; chosen after the English Dutch Wars where both sides stopped for Church on a Sunday. A similar church pennant is flown by U.S. Navy ships during services.
A senior officer present afloat pennant using the NATO signal flag for "starboard" is green on the hoist and fly with a white field between.
A gin pennant means that the wardroom is inviting officers from ships in company to drinks. The origins of the gin pennant are uncertain, but it seems to have been used since the 1940s and probably earlier. Originally it was a small green triangular pennant measuring approximately, defaced with a white wine glass; nowadays the gin pennant is the "starboard" manoeuvering signal pennant defaced with a wine or cocktail glass. Its colour, size and position when hoisted were all significant as the aim was for the pennant to be as inconspicuous as possible, thereby having fewer ships sight it and subsequently accept the invitation for drinks. The gin pennant is still in regular use by Commonwealth navies, such as the Royal Australian Navy. Within the RAN it is common practice, whilst in port, for junior officers of one ship to attempt to raise the gin pennant on the halyard of another ship, thereby forcing that ship to put on free drinks for the officers of the ship that managed to raise the pennant. If, however the junior officers are caught raising the pennant, then it is their ship that must put on free drinks within their Wardroom. Usually this practice is restricted to Commonwealth navies.
Broad pennant
House flag

Merchant ships often fly a flag identifying which company owns the vessel. This was formerly flown from the mainmast but is now usually flown from the jackstaff.

Private signal

Private signals are custom designed flags used to symbolize and identify the owner of a boat.

Yacht club burgee

Members belonging to a yacht club or sailing organization may fly their club's unique burgee both while underway and at anchor. Sailing vessels may fly the burgee from the main masthead or from a lanyard under the starboard spreader on the mast. Power boats fly the burgee off a short staff on the bow.

Unit citations

Warships of various navies may be awarded a unit citation, for which a burgee is flown when in port.

Ships of the United States Navy:
* Presidential Unit Citation: yellow with blue stripe on top and red stripe at the bottom.
* Navy Meritorious Unit Commendation: green with four yellow stripes divided by two blue and one red stripes at the centre.
* Navy Unit Commendation: symmetrical colouring from the centre: green, red, yellow, blue.
Ships of the Royal Australian Navy may have:
* Unit Citation for Gallantry: burgee with narrow white band surrounding green field surmounted by a silver star.
* Meritorious Unit Citation: design as above with yellow field.
Signal flags

There is a system of International maritime signal flags for each letter of the alphabet, and pennants for the numerals. Each flag has an additional meaning when flown individually, and they take other meanings in certain combinations.

Courtesy flag

A courtesy flag is flown by a visiting ship in foreign waters as a token of respect. It is often a small national maritime flag of the host country, although there are countries where the national, rather than the maritime flag is correct. The flag is customarily worn at the foremasthead of multi-masted vessels, the dockside yardarm or crosstree of the mast of single-masted vessels, while the house flag would be outboard. It may be flown from the jackstaff of vessels without masts.