Similar term(s): FOC, open registry, flag of necessity.
The flag of a country with easy or lax maritime regulations and low fees and taxes, flown by ships that register their vessels in such countries, even though their ownership and main cruising areas are elsewhere.
Source:
Home-Based Travel Agent Resource Center
Dictionary
Flag of convenience is also called "open registry", because the register is open to foreign shipowners.
Source: GreenFacts, based on PortCities Southampton
Glossary