Northwest Airlines has decided to plead guilty for its role in fixing air-cargo prices.

The US Department of Justice has said the company will pay a $38 million fine as part of a plea deal.

Northwest will also co-operate with the ongoing anti-trust investigation into its former subsidiary, Northwest Airlines Cargo, which is no longer operating.

The accusation is that Northwest Airlines Cargo conspired to fix air-cargo rates from July 2004 to February 2006, before a take over by Delta Air Lines in October 2008.

Northwest has agreed to plead guilty to a single offence that also involves another 16 airlines, which have already pleaded guilty or agreed to do so.

Four executives have already received prison sentences as a part of the ongoing investigation.