The Tongan government says any new airline entering the domestic market must include the two Niuas in its network.
The transport minister, Samiu Vaipulu, has told Radio Tonga that a carrier cannot limit its service to Vava'u and Ha'apai.
Mr Vaipulu referred to Palu Aviation which plans to launch flights to just Vava'u and Ha'apai.
The airline brought in an aircraft four months ago but is still awaiting a licence.
Mr Vaipulu says the company hasn't completed the required paperwork on technical information and its finances.
The CEO of Palu Aviation, Tevita Palu, has denied this.