It has since reached an agreement with Portugal's government whereby the state is to retain a 50% stake in TAP.

The Hainan deal, which was struck at $450 million (€403 million), makes it Azul's largest shareholder, according to a statement released by the Chinese company.

"We see Azul as a strong partner in the long term for [Hainan] HNA to expand and invest in Latin America," the statement quoted Adam Tan, the company's chief executive, as saying.

Last year, Hainan paid €30 million for 25% of TAP's convertible bonds.

In the same month it announced the acquisition for $1.5 billion of Switzerland-based Gategroup Holding, the world's second largest aviation catering business.

Hainan Airlines is to cooperate with Azul with code sharing for flights, the opening of new routes, marketing and transport tariffs, according to the statement.

The company, which is based on the island of Hainan, in the far south of China, also has activities in the industrial, tourism, logistics and financial sectors.

China's central government has encouraged companies to invest abroad, as a means of securing raw materials and reliable returns on investment, against a backdrop of a slowdown in the domestic economy.

This week China's Fosun group, which has already invested almost €1.5 billion in Portugal, in the insurer Fidelidade, the healthcare group Luz Saúde and a 5.3% stake in energy grid operator Redes Energéticas Nacionais (REN), announced the acquisition of the Brazilian investment fund manager Rio Bravo. It is also known to be mulling the acquisition of a major stake in BCP, one of Portugal's largest banks.