Travelers look at the boarding information at Beijing Capital International Airport on June 13 in Beijing. Photo: IC

The past half year has been a promising one for China's major airlines as they shake off the shadow of gloomy profits.

More network expansion, more cooperation and lower fuel prices are supposed to trigger another round of sizable profits for the carriers.

Although the second quarter figures have yet to be released, the first quarter numbers give an idea about what to expect.

China's four major airlines - Air China, China Southern, China Eastern and Hainan Airlines - all reported that their net profits jumped by more than 40 percent year-on-year in the first quarter.

China Eastern's profits soared by 66.37 percent, the fastest among the four airlines.

Meanwhile, China Southern reported the highest profit of its peers - 2.68 billion yuan ($400 million).

For the coming annual results, Air China said in its first quarter report that stable growth, a rising number of passengers and low fuel prices have provided them with opportunities.

The past six months have seen network expansion in different continents, and the pace has not slowed.

In the latest example, Shanghai-based China Eastern has sped up its expansion in Europe. In one week, it opened four routes, extending its network to St. Petersburg, Prague, Amsterdam and Madrid. It now has nine destinations in Europe.

Hainan Airlines just opened a route from Beijing to Calgary, Canada, at the end of June, following routes from Beijing to Tel Aviv, Changsha, capital of Central China's Hunan Province, to Los Angeles, and Beijing to Manchester earlier this year.

China Southern said it now flies to 71 cities in 38 countries and regions with 166 routes, compared with 52 cities in 33 countries and regions with 115 routes before March 2015.

International transport capacity grew by 19.4 percent year-on-year in April, according to the latest data provided by the Civil Aviation Administration of China (CAAC).

Another highlight for the industry has been its growing cooperation with foreign and domestic investors.

China Eastern raised 8.55 billion yuan in a private sale of shares to a group of investors including Ctrip, China's biggest online travel agency, which became the airline's fifth largest shareholder, Reuters noted Tuesday.

In an interview with the Financial Times on Monday, Chen Feng, the chairman of HNA Group, Hainan Airlines' parent company, said it is looking to do more deals.

This year, HNA announced several deals, including the acquisition of Ingram Micro, a US information technology company, Carlson Hotels, the US owner of the Radisson hotel chain, and a 13 percent stake in Virgin Australia, the Australian airline.

The airlines have also introduced more aircraft this year to woo passengers with better services.

China Eastern now has 85 aircraft, including 30 Airbus A330s, 20 Boeing 777-300ERs, 20 Airbus A350-900s and 15 Boeing 787-9s. Air China received its first Boeing 787-9 in May, and it is expected to receive seven more by the end of October.

In June, Hainan Airlines took delivery of its first 787-9, and is scheduled to receive eight more in 2016.

In total, the four airlines will take delivery of 22 wide-body aircraft this year, 18 wide-body aircraft in 2017 and 37 in 2018.

According to a CAAC statement, 49 airlines - 16 domestic and 33 foreign - were issued certificates for international routes in the second quarter of this year. They received approval for 132 routes, including 67 routes operated by overseas carriers.

Budget airline Peach Aviation will fly from Osaka to Shanghai and Tokyo to Shanghai.

Although Chinese airlines control half the market for commercial flights between China and the US, they still need to keep an eye on the market for second-tier Chinese cities as more and more US airlines are making inroads there.

Also, established overseas players, especially from the Middle East, could also threaten the business of Chinese carriers.

In recent years, airlines including Emirates, Etihad Airways, Qatar Airways and Turkish Airlines have been investing in building transfer airports to seize passengers from Asia and Europe, which has threatened some established players such as Lufthansa and Air France.

Also, airlines ought to think hard about how they can ensure the profitability of their long-haul routes, as it takes a long time to cultivate the market.