Maritime flag

The Red Ensign, as currently used by the United Kingdom's Merchant Navy

Ensigns are usually required to be flown when entering and leaving harbour, when sailing through foreign waters, and when the ship is signalled to do so by a warship. Warships usually fly their ensigns between the morning colours ceremony and sunset when moored or at anchor, at all times when underway, and at all times when engaged in battle—the "battle ensign". When engaged in battle a warship often flies multiple battle ensigns. This tradition dates from the era of sailing vessels. 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 flown in order to keep the ensign flying even after a mast hit.

Jacks are additional national flags flown by warships (and certain other vessels) at the head of the ship. These are usually flown while not underway and when the ship is dressed on special occasions. Jacks in the Royal Navy must be run up when the first line is ashore when coming alongside.

The flag of the National Oceanic and Atmospheric Administration, flown by all commissioned NOAA ships as a "distinguishing mark"

On 16 January 1899, commissioned ships of the United States Coast and Geodetic Survey were authorized to fly their own flag to distinguish them from ships of the United States Navy, with which they shared a common ensign. Although they continued to fly the same ensign as U.S. Navy ships, ships of the Survey flew the Coast and Geodetic Survey flag as a "distinguishing mark" until the newly created National Oceanic and Atmospheric Administration (NOAA) took over control of the Survey's ships in 1970. Since then, commissioned ships of NOAA, which also fly the same national ensign as U.S. Navy ships, have flown the flag of the National Oceanic and Atmospheric Administration as a distinguishing mark.

Similarly, all ships of the United States Lighthouse Service flew the U.S. Lighthouse Service flag until the service merged into the United States Coast Guard on 1 July 1939,[1] and ships of the United States Bureau of Fisheries flew the Bureau of Fisheries flag until the bureau was merged into the United States Fish and Wildlife Service on 30 June 1940.

Rank flag of a Rear Admiral of the Indian Navy.

The rank flag or distinguishing flag is the flag flown by a superior officer on his flagship or headquarters (hence the term flagship). 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 flown when leaders of the government (presidents, prime ministers or defense secretaries) 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 (Manning the rails, firing cannon salute, attention, etc.) 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 fly 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 one and two 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 (upper quarter next to the staff).
• In the United States Navy as well as in 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 Hellenic Navy (Greek Navy) Admirals fly blue square flags bearing a white cross (similar to the Hellenic Navy Jack) with four six-point stars (one in each of the squares formed by the cross); 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 (square swallow-tailed flag) with the colours of Hellenic Navy Jack. When a rank flag is flown the commissioning pennant is displaced downward.

The church pennant of the Royal Navy, Royal Netherlands Navy and the Royal Australian Navy

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 (and thus of the ship itself). 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. 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 (bases) 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 18 by 9 inches (460 by 230 mm), defaced with a white wine glass, nowadays the gin pennant is a Starboard 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 (RAN). 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; however, prior to increased force protection, RAN officers have successfully raised the Gin Pennant on a number of units in the USN.

House flags, ca. 1900

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

Burgee of Barrachois Harbour Yacht Club, Nova Scotia, Canada

Members belonging to a yacht club or sailing organization may fly their club's unique burgee both while underway and at anchor (however, not while racing). Sailing vessels may fly the burgee from the main masthead or from a lanyard under the starboard spreader on the mast.[2] Power boats fly the burgee off a short staff on the bow.

Warships of various navies may be awarded a unit citation, for which a burgee (tapering flag with swallow-tail fly) 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.

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

A courtesy flag (or courtesy ensign) is flown by a visiting ship in foreign waters as a token of respect. It is often a small (that is, smaller than the ship's own national ensign) national maritime flag of the host country, although there are countries (such as Malta) 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.

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  A courtesy Turkish flag is raised aboard the destroyer USS Truxtun as the ship transits the Bosphorus strait
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  Superyacht Ariane NI in Toulon harbour, flying her British ensign and a French courtesy flag
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  The frigate Hermione moored in New York in 2015, flying the Betsy Ross flag and the Serapis flag, two early US flags and ensigns.
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  HMS Boadicea flying a courtesy Imperial Russian Navy Ensign during an official visit to Kronstadt in June 1914

As a sign of celebration, ships in harbour may be dressed overall.