HNA and COMAC said in a statement that they had signed a strategic cooperation under which HNA had agreed to introduce and operate the jets in China and in overseas markets such as Africa over an unspecified period of time.

It did not disclose financial terms or say whether these were firm orders or options.

The Chinese conglomerate, which has been selling assets to raise cash, holds stakes in over ten airlines, including Hainan Airlines, Capital Airlines and Africa World Airlines in Ghana. It signed a deal for 15 C919 planes in 2010.

HNA said it had signed the deal to support the development of China's aviation industry as well as Beijing-led "Made in China 2025" and Belt and Road initiatives, it said.

The C919 aircraft is a symbol of China's ambition to muscle into a global jet market estimated to be worth $2 trillion over the next two decades, as well as of Beijing's broader "Made in China 2025" plan to spur home-made products, from medicines to robots.

The state planemaker sent the C919 narrowbody plane on its maiden flight last year and obtained approval to begin mass production of the ARJ-21 regional jet last July.

In February, COMAC said its total order book for the C919 jet was 815 aircraft, while orders for the ARJ21 stood at 453.

(Reporting by Brenda Goh; Editing by Andrew Bolton)