DUBAI (Reuters) - The chairman of Dubai carrier Emirates said on Tuesday he was not happy with Boeing ( BA ), which he said had promised him that it would fix issues plaguing the U.S. planemaker, including its 777X program.

Emirates is the biggest customer of Boeing's ( BA ) 777X, which will be the industry's largest twin-engined jet with around 400 seats. But its entry into service has been delayed by about five years due to problems including certification delays.

Sheikh Ahmed bin Saeed Al Maktoum, a key member of Dubai's ruling family and member of government, said he believed the certification would now happen in the first quarter of 2025.

But he said the uncertainty over when it would be delivered was putting pressure on Emirates, by far the Middle East's biggest airline and which only uses large twin-engined jets.

Sheikh Ahmed said the airline would keep using existing jets for longer than expected as a result of the 777X delays.

"I'm not happy," he told reporters at the Arabian Travel Market tourism trade exhibition in Dubai.

"They promised they would do their best to fix it," he said of Boeing's ( BA ) new management when asked about the issues it faces.

Boeing ( BA ) is overhauling its management amid mounting pressure from airlines, regulators and investors as it grapples with a growing crisis following a January mid-air panel blowout on a 737 MAX plane.

(Reporting by Alexander Cornwell; Editing by Emelia Sithole-Matarise)