Flag of convenience is a word from shipping. Every ship needs to be registered in a port. The laws of the port are valid for the ship's crew. In some countries the rules are not as strict as in others, or they are cheaper to use. Many owners of ships from other countries register their ships in one of those easy or cheap countries. The ship might never even come anywhere near that country, but it must fly the flag of the country where it was registered. This is then called a flag of convenience. Among the most popular flags are Panama, Marshall Islands and Liberia.