The planned withdrawal of China Southern Airlines Co, the largest airline by fleet size in Asia, from the SkyTeam airline alliance signifies less close-knit alliances and more cross-alliance cooperation, analysts said.

China Southern announced on Thursday it would not renew its SkyTeam membership when it expires on Jan 1 next year "based on the needs of the company's development strategy and to better align with the new trend of cooperation in the global aviation industry".

It will "explore the possibilities to establish new partnerships with advanced airlines, promote bilateral and multilateral cooperation and provide quality services to passengers around the world".

The carrier on Monday pledged to work closely with SkyTeam on a cooperative process during the transition period ending on Dec 31, 2019, during which its passengers will be entitled to all SkyTeam services but it will not sell SkyTeam-related products.

Star Alliance, SkyTeam and Oneworld are the three largest global airline alliances. However, cross-alliance investment and cooperation have been on the rise in the past few years.

China Southern signed an agreement last year to sell a minority stake to American Airlines Group Inc, which belongs to Oneworld.

China Eastern Airlines Corp, a SkyTeam member, announced in August it will jointly operate more flights with Japan Airlines Co, which is a Oneworld member.

"The independent operation of airlines is becoming a new trend. China Southern has a huge market in China, and it can easily find cooperation partners. It would be more flexible for it to cooperate with different airlines and seek cross-alliance cooperation, without being tied to any particular alliance," said Zou Jianjun, a professor at the Civil Aviation Management Institute of China.

Zou said it was unlikely that China Southern would join Oneworld, as joining an alliance is not an essential measure for China Southern to carry out cooperation.

"At SkyTeam, China Southern has contributed more than it has received. With its rich domestic flight network, a group of foreign airlines have been seeking support from China Southern. However, the growth of China Southern's international flights is unsatisfactory, and it barely seeks assistance from foreign airlines," he said.

The withdrawal of China Southern from SkyTeam is aimed at increasing its international operations while avoiding competition with China Eastern in international flights within the alliance, said Xu Shuo, a researcher with Qianzhan Industry Research Institute.

As the second-largest airline in SkyTeam, China Southern has not received much support in the alliance for its North American flights, due to the close ties between two other SkyTeam members, China Eastern and Delta Airlines, Xu said.