A fourth airline has pleaded guilty to participating in a cartel that fixed the price of air cargo, Canada's Competition Bureau said Tuesday.

Qantas Airways Ltd. was fined $155,000 after it  admitted that its freight division fixed surcharges on cargo exported on certain routes from Canada between May 2002 and February 2006, the bureau said.

"During most or all of this period, Qantas Freight trucked cargo from Canada to the United States for onward shipment to Australia and other destinations," the bureau said.

On June 26, the regulator said that three related airlines — Air France, KLM and Martinair — were fined a total of $10 million after pleading guilty on similar charges.

The Canadian fines follow penalties already levied by other countries against many airlines for cargo price-fixing.

The U.S. Justice Department has fined 15 airlines more than $1.6 billion US, and three executives had been sentenced to jail time, the department announced in April.

In Australia, regulators have fined Air France-KLM, Martinair Singapore Airlines, Qantas and British Airways PLC.

The bureau investigation is continuing.

Under the Competition Act, any agreement between competitors to fix prices that produces an "undue" reduction in competition in Canada is a criminal offence, the bureau said.