The Fiji-based airline, Air Fiji, is protesting against the government's decision to revoke its licence to service the Tonga route.
Air Fiji has been replaced on the route by Air Pacific, which is majority owned by the Fiji government.
Air Fiji's chief executive, Sialeni Vuetaki, has told the Fiji Times the Fiji government's reason is that the smaller, mainly domestic carrier is not majority Fiji owned.
Air Fiji has been majority owned by the Tuvalu government for several years and Mr Vuetaki says the shareholding has not changed since the Tonga route licence was issued.
He says Air Fiji is losing over 1.2 million US dollars in income as a result of the Fiji government's sudden decision.