Quarantine "yellow jack" but this was also a name for yellow fever, which probably derives its common name from the flag, not the color of the victims (cholera ships also used a yellow flag). The plain yellow flag ("Quebec" or Q in international maritime signal flags) probably derives its letter symbol for its initial use in "quarantine", but this flag in modern times indicates the opposite—a ship that declares itself free of quarantinable disease, and requests boarding and routine port inspection. Australia has perhaps the world's strictest quarantine standards. Quarantine in northern Australia is important because of its proximity to South-east
Maritime flag which a burgee (tapering flag with swallow-tail fly) is flown when in port. 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