Hijacking of jetliner is a windfall for South Korea's relations with China

When six Chinese defectors hijacked a domestic airliner to South Korea last week, they unwittingly initiated a breakthrough in Chinese-South Korean relations.

The airliner, a British-built Trident with 105 people on board, was on a scheduled flight from Shenyang in Manchuria to Shanghai. An hour after takeoff, the hijackers shot their way into the cockpit and eventually forced the pilot to land the plane in South Korea.

But as the immediate drama of the situation faded, it was replaced by excitement over the longer-term implications of the incident. From the South Korean point of view, better relations with North Korea's main ally could help to lessen tension on the divided peninsula and would considerably strengthen the south's position vis-a-vis North Korea.

China and South Korea do not have diplomatic relations. The Chinese fought against South Korea in the 1950-53 Korean war and have continued to support the north. So when Shen Tu, the director general of the Civil Aviation Authority of China, sent a message to the South Korean government asking for permission to come to Seoul to personally conduct negotiations on the hijacking, it was the first official contact between the Republic of Korea and communist China.

The arrival in Seoul last Saturday of a 33-man party from Peking and the ensuing talks were viewed with optimism. The negotiations marked the first face-to-face confrontations between South Korea and China. After several rounds of talks, South Korea's Foreign Ministry announced that the two nine-member delegations had agreed on the return to China of the plane, passengers, and crew as soon as possible. This was the first official agreement between the nations.

But inevitably there was a fly in the ointment - in this case the fate of the hijackers, five Chinese men and one woman. South Korea has decided to exercise its legal right in accordance with international laws to try the six hijackers in Korea.

There was no official comment on China's reaction to this decision but Korea's chief negotiator, Assistant Foreign Minister Kong Ro-Myung, told reporters, ''No Western countries have returned hijackers. And the Chinese seemed to be aware of this.''

During the course of the talks, the South Koreans went out of their way to impress their unexpected Chinese guests. The passengers and crew of the Trident were accommodated in a luxury hotel in Seoul; the crew declined sightseeing tours, saying it only wanted to go home. But most of the 87 Mao-suited passengers, looking slightly overwhelmed by the turn of events, were entertained lavishly, taken to tourist spots, department stores, and plied with gifts.

Although there have been no official relations, contacts between the two countries have increased recently, and there has been significant trading - $600 million worth in 1980, say businessmen here. Hong Kong companies often acted as intermediaries.

Two weeks ago, South Korea for the first time admitted to an exchange of visits with China, reporting that 23 South Koreans had visited China since President Chun Doo Hwan came to power in 1980 and 11 Chinese had visited South Korea since 1981.