The phrase "flagship" refers to the most important or prestigious product or service that a company offers. It is often the finest example of what the company has to offer and is used to represent the company's brand or image. Full definition
We start out with our convictions like flag ships; wanting only to share the good news, change the world, and impact lives. (nakedpastor.com)
My guess, without reading the relevant treaties, is that consent to jurisdiction by the country under whose flag the ship operates subjects a ship to the treaty. (law.stackexchange.com)
(Gothenburg, Sweden, 7 May, 2015): WWF's flag ship business programme Climate Savers is marking 15 years of corporate leadership in reducing greenhouse gas (GHG) emissions by introducing a new measuring standard, reflecting the global shift in the role of business in fighting climate change. (climatesavers.org)