This follows comments by Turkey's Prime Minister Tayyip Erdogan at the weekend that the two companies were to deepen existing ties. Erdogan said on Saturday he had agreed to a proposal by German Chancellor Angela Merkel to establish "joint management" of the two carriers.

"Now it is a matter of advancing this cooperation somewhat further," Milliyet newspaper quoted Turkish Airlines THY.Lchairman Hamdi Topcu as saying. "We discussed this subject in communication with the Lufthansa side. The Lufthansa management shared this communication with German Chancellor Angela Merkel."

"On Monday we in the THY management will talk this subject over. But the dimension of the cooperation is not yet clear," Topcu said.

Turkish Airlines rose as much as 5 percent in Istanbul and were 4.55 percent higher at 4.37 lira at 0836 GMT.

The tough economic climate has pushed a number of airlines to form partnerships to cope with the difficult conditions.

Turkish Airlines and Lufthansa are joint owners of the SunExpress airline and members of the Star Alliance, one of the global airline networks.

"The structure of a possible cooperation is vague for the time being," Oyak Securities analyst Alper Ozdemir said in a note.

"While we do not expect anything material to come out in the short term, expectations for any type of cooperation that will better both operators will support the share price," he said.

Lufthansa spokesman Klaus Walther said on Saturday: "We are always in talks about how we can further improve and intensify the cooperation between Lufthansa and Turkish Airlines for the benefit of our customers," he said.

A Turkish Privatisation Administration official said in late September there had been no decision on the method or size of a sale of some of the government's 49.12 percent stake in Turkish Airlines after a newspaper reported the state planned a 30 percent block sale.

Lufthansa is in the middle of a 1.5 billion euro cost-cutting programme to combat rising fuel costs and increased competition from low-cost and Gulf rivals. It has said the programme was needed so it can afford new fuel-efficient planes and that is its focus at present rather than any acquisitions.

(Writing by Daren Butler; Editing by Dan Lalor and Jane Merriman)

• A Permanent Economic Emergency