noun
coastal route; domestic sea route
Refers to a shipping route within a country's own waters, as opposed to international routes (外国航路).
See also: 外国航路
この港は内国航路の拠点として使われている。
This port is used as a hub for domestic sea routes.
外国航路 means international sea route, while 内国航路 means domestic or coastal route.
Compound of 内国 (domestic) and 航路 (sea route).