A New Zealand court has ordered Australian airlines Qantas to pay fines worth NZ$6.5 million for fault of price fixing, records showed.

The country's competition watchdog announced on Thursday, the penalty-"the highest yet for price fixing"-was actually proposed by Qantas as part of a pre-trial settlement in an air cargo cartel case and has now been confirmed by the High Court, the Commerce Commission said.

The judge noted the starting point for the penalty was NZ$13 million. Nevertheless, a 50 percent discount was given Qantas for its high level co-operation with the investigation.

"As soon as the nature and scale of the problem came to the notice of Qantas senior management and its board, the commission was advised that Qantas would cooperate in every respect," Justice Allan said in his judgment.

"It has continued to do so over a significant period. In particular, it has pro-actively provided extensive evidence and documents detailing the collusive FSU (Fuel Surcharge Understanding) and its own participation in that FSU," the court documents indicated.

The Commerce Commission is also tackling another case investigating cartel proceedings in which several international airlines are accused of colluding to raise the price of freight.