Singapore Airlines Ltd., the world’s biggest airline by market value, said its cargo unit is offering pilots as much as 30 months’ unpaid leave because of slumping air-freight demand. The cargo unit is also planning to park some aircraft over the next few months, airline spokesman Stephen Forshaw said in an e-mail. The airline’s passenger unit isn’t planning any similar steps at present, he added.

Singapore Airlines joins Cathay Pacific Airways Ltd. in offering employees unpaid leave, as airlines battle to cut costs amid slowing demand. Global freight traffic fell 13.5 percent last month from a year earlier, the sixth straight decline, while passenger traffic dropped for the third month in a row, the International Air Transport Association said.

“SIA Cargo needs to do all it can to contain costs,” Forshaw said. The freight unit has about 300 pilots, while Singapore Airlines employs about 2,000 pilots, the Business Times said today, when reporting the plans.

The cargo unit posted an operating loss of S$76 million ($53 million) in the six months ended September, compared with a S$19 million profit a year earlier, the airline said in November. Singapore Airlines started the cargo division in 1992. The unit operates 14 Boeing Co. 747-400F freighters as well as using capacity on Singapore Airlines’ passenger aircraft, according to the company’s Web Site.