Industry sources said some airlines that own new-generation 737s, particularly 737-700s and 737-800s, have received instructions to check the modules.

At its worst, the malfunction may cause planes to crash.

Comments from the airlines and the country's aviation regulator, the General Administration of Civil Aviation of China (CAAC), were not available yesterday.

Boeing released a statement yesterday saying it had become aware of problems with its 737s and is discussing possible remedies with airlines.

Airlines were instructed to check the serial numbers on the modules - there are two in each plane.

If both numbers are within an identified series, Boeing recommends operators take the plane out of service and replace a part in the module.

If only one of the numbers is within the series, operators are instructed to perform two specific preflight checks to ensure it is operating properly.

Boeing says fewer than 50 of the 737s within a fleet of more than 1,300 may be affected.

The announcement was made to all Boeing customers. It is still not known how many planes in China are affected.

The Beijing Morning Post reported yesterday a scheduled flight between Beijing and Shanghai was cancelled yesterday morning because of concerns the 737-700 might be open to the module failure.

The report said officials with the carrier, China Eastern Airlines, confirmed the newly-delivered plane might have the technical pitfall.

It is the second major problem for the Boeing within two weeks.

Earlier this month, Boeing said the oil pumps on some of its planes could pose threats to flight safety. CAAC officials responded by saying they will order checks on all pumps.

Passengers seem to be fairly sensitive to reports about technical glitches and many of them have said they are worried about safety issues.

A businessman who did not give his name said Boeing should run more trials before selling its planes.

The problem with the module was publicized on Friday when the US Federal Aviation Administration (FAA) issued a statement about the possible defect.

The FAA required immediate inspections of the newer models before they would be allowed back in the air.

The inspections cover about 100 planes and airlines must also check their inventories of parts.

The 737 series is the world's most widely used commercial plane with 2,000 registered to US airlines and another 4,500 in service throughout the rest of the world.

There are 223 Boeing 737s in service in the Chinese mainland, accounting for nearly half of the domestic fleet.

(China Daily September 17, 2002 )