The Tongan government says a law permitting airline flights on Sundays if there is a disruption to Saturday's schedule is already in place.
An Air New Zealand flight on which five and a half tonnes of fish were scheduled to be exported was cancelled two Saturdays ago after an eruption on Hunga Ha'apai Island.
The Fishing Industry Association says with the fish worth between 20 and 30 thousand US dollars a tonne, the sector can ill afford the sort of losses the cancellation incurred.
The Minister for Transport, Paul Karalus, says the government will reiterate that provision for such incidents already exists.
"We are very much cognisant of this need for there to be as much done as possible to ensure that the industry is able to get its product out of the country. I am working on this at the moment to get the cabinet decision that actually outlines that and like I say the airport operator and the airport ground handlers and that are fully aware of it but it seems that this airline in particular is not."
Paul Karalus, the Minster for Transport in Tonga.