Image caption Northwest merged with rival Delta in 2008

Northwest Airlines is to plead guilty and pay a $38m (£24m) fine for its role in fixing air-cargo prices, the US Department of Justice has said.

The department said as part of a plea deal Northwest would co-operate with an ongoing anti-trust investigation.

Northwest Airlines Cargo, which is no longer operating, conspired to fix air-cargo rates from July 2004 to February 2006, the department added.

Northwest was taken over by Delta Air Lines in a £1.7bn deal in October 2008.

Northwest has agreed to plead guilty to a single offence, said the DoJ.

So far a total of 16 airlines have pleaded guilty or agreed to do so in an ongoing investigation into price-fixing in air cargo, it added.

More than $1.6bn in criminal fines has been paid by airlines, and four executives have received prison sentences.