HANOI (Reuters) -Vietnamese low-cost carrier Vietjet stopped operating two Chinese-made COMAC C909 aircraft on October 18 after a six-month lease contract for the planes expired, two sources familiar with the matter said.

The C909s were introduced in Vietnam less than a week after Chinese President Xi Jinping visited Hanoi in April, highlighting the political significance of the launch as a gesture of deepening strategic and economic ties between the two countries.

However, Vietjet has opted not to extend the lease and has no immediate plans to purchase aircraft from China's state-owned planemaker COMAC, the two sources said. Vietjet declined to comment, while COMAC did not respond to a request for comment.

CONTRACT HAD BEEN MAJOR BREAKTHROUGH FOR COMAC

The lease marked the first use of Chinese aircraft on domestic routes in Vietnam including Hanoi-Con Dao and Ho Chi Minh City-Con Dao, and was a major breakthrough for COMAC, which has struggled to have its planes used abroad.

One of the sources said the termination was due to high operational costs linked to foreign crew and maintenance services, and regulatory constraints under Vietnam's aviation laws. Vietjet had an agreement for the jets to be operated by crew from China's Chengdu Airlines, Reuters has reported.

The source said the airline may switch to a different leasing model in the future.

Chengdu Airlines also did not respond to a request for comment.

Both sources emphasized that there were no operational issues with the COMAC aircraft during their tenure in Vietnam.

The aircraft made their final flights on Friday, traveling from Con Dao to Hanoi, according to flight tracking website FlightRadar24.

C909 IS CHINA'S FIRST COMMERCIALLY PRODUCED JET

The C909, previously branded as the ARJ21, seats up to 90 passengers and is China's first jet-powered plane to reach commercial production, entering service in 2016.

COMAC has been positioning its C909 regional jets in Southeast Asia as a foothold in foreign markets, with placements in Indonesia, Vietnam, and Laos, as well as orders from Air Cambodia and an airline in Brunei.

Vietjet, which operates a fleet of over 100 aircraft, primarily Airbus models, has also placed significant orders for Boeing 737 MAX jets.