It was reported that the same aircraft and crew had been involved in an earlier hijack in May 1988, when two men forced the plane to Taiwan.

According to reports, the pilot had his flying licence suspended and his meal allowance and bonuses stopped for eight months as punishment for what was seen by Chinese authorities as mishandling of the incident.

The source said that after that punishment, ''he had no incentive the next time around to go to Taipei''.

Chinese officials were called to task for disciplining the pilot after the 1988 incident and there was a policy change as a result of the Guangzhou crash, he added.

A directive, in line with international practice, was put out telling air crews: ''Don't resist a hijacker, follow his orders.'' Yesterday's incident showed the previous, aggressive policy towards hijackers ''has probably changed'', said Mr Steve Miller, managing director of consultancy and leasing company Trinity Aviation.

Chinese crews and authorities have a history of taking tough action against hijackers, allegedly producing a string of dramatic mid-air battles.

In July 1982 crew members and passengers reportedly beat into submission five hijackers who ordered the crew to fly them to Taiwan.

The crew members were offered medals and pay rises by the Chinese authorities as a reward. The pilot was given the title Anti-Hijack Hero, as the five hijackers were led to their executions.

A Hongkong magazine reported that a pilot killed a hijacker with a spanner in a separate incident the same month.

In February 1983 a Chinese pilot who tried to hijack a domestic flight to Taiwan was shot and killed in a cabin brawl, and in January the same year a Hongkong newspaper reported that one person was killed after a fight during a hijack attempt.

There were reports in September 1982 of a jetliner crashing in Guangxi, killing 112 people, after the pilots attempted to stop a hijacking.

It is believed China may have once put armed guards on planes - but no longer does. In 1987, China announced it had developed a lightweight pistol designed to shoot hijackers without penetrating plane windows or walls. Meanwhile, martial arts experts trained Chinese Air Force personnel to fight hijackers.

Experts said yesterday that China Southern Airlines was considered a good-quality carrier by Chinese standards.

''It's a very reputable airline. In my opinion, it's extremely well run,'' said Mr Jim Eckes, an aviation consultant with Indoswiss Aviation.

But security is the responsibility of airport officials, not airlines.

The newness of Shenzhen airport, which has become China's fourth busiest after less than 18 months' operation, may have contributed to a security lapse, the industry source claimed.

''Until you have a hijack, generally speaking, people working on security are not as alert,'' he said.

Chinese officials dismissed reports that a China Southern Airlines Boeing 737 which crashed near Guilin in November had been hijacked, and that pilots had engaged in a fight with hijackers.

A Boeing spokesman said yesterday that Chinese authorities, assisted by Boeing and US air safety officials, were continuing to investigate the cause of the crash, which killed 141.