Tonga's Civil Aviation Department says a World Bank report on the transport industry is wrong.
The report has not been published yet, as the World Bank is awaiting an official response from Tonga.
It was commissioned by the Tongan Prime Minister Lord Tu'ivakano and the New Zealand Foreign Minister, Murray McCully, in March.
It was hoped the industry-wide review would solve the ongoing dispute between the countries around the MA60 aircraft gifted from China to Tonga.
But the report's conclusion that the MA60 was not properly certified will be contested by Tonga's Civil Aviation Division.
The CEO, Vili Cocker, says everything was done in accordance with the regulations of the International Civil Aviation Organisation, and the World Bank never approached it to ask for the documentation.
"We're not happy with it, because they did not include our division, and our minister in the consultations and the interviews, and we have the record of those assessments that we did."
Vili Cocker of Tonga's Civil Aviation Department