FRANKFURT (Reuters) - Lufthansa Cargo <LHAG.DE> is battling with one of the worst yield crises it's ever seen, caused by slowing global trade and overcapacity in the market, the freight carrier's chief executive said.

"Yields, or the average price per kilogram of freight, are down 15-20 percent compared with last year, it's a landslide," Peter Gerber said at an event in Frankfurt.

Lufthansa Cargo, the freight arm of Lufthansa, currently runs a fleet of 12 MD-11 and 5 777F freighter planes. Due to overcapacity, it has parked a further two MD-11s and is cutting up to 800 jobs in a bid to reduce costs.

"For the moment, our fleet is the right size, although we don't know how the future will develop," Gerber told Reuters.

He added Britain's vote to leave the European Union was not causing him any additional worries.

(Reporting by Victoria Bryan; Editing by Tina Bellon)