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
Flag protocol ceremonial flypast, a flag is flown from a weighted rope dangling from beneath a helicopter. Members of the royal family and the nobility each have their own flags. The Standard of the Sultan must be flown only over Istana Nurul Iman. The same goes for the Crown Prince (Deputy Sultan)'s flag, but other non-royal title holders fly the national flag. As in many other countries, Bruneians consider it taboo for the flag to touch the ground. When a French vessel meets another French ship, it is to lower and raise its ensign as a greeting. A merchant ship meeting a