Turkish Airlines’ plan to order more than 200 Boeing Co. jets is being held up by differences with engine supplier General Electric Co. over maintenance costs. 

The carrier is pressing GE to lower its demands on maintenance, Chairman Ahmet Bolat said Tuesday in an interview with Bloomberg TV at the Farnborough International Airshow outside of London. “Once they move, we will sign the deal,” Bolat said. 

A deal with Boeing would follow a commitment for 230 Airbus planes made in December, as Turkish aims to cement its position as a global aviation powerhouse. The carrier has said publicly for months that it wants to place a major Boeing order as it aims to almost double its fleet in the next decade. 

Turkey’s flag-carrier is looking to buy as many as 175 Boeing 737 Max jets, with the rest of the order made up of the larger 787 Dreamliner model.

The chairman said on a panel Monday that he spoke with GE counterparts at Farnborough and the two sides are close, but an order won’t be announced at the event.

Turkish is still looking to expand capacity and resorting to using older aircraft to substitute till newer jets are delivered, Bolat said.