US federal regulators ordered inspections of the wing slats on all newer Boeing 737 jetliners based on findings about a fire that destroyed a China Airlines 737 in Japan recently.

The orders apply to the owners and operators of 783 US-registered airplanes but probably will be imposed by other countries on the worldwide fleet of 2,287 newer 737s, Federal Aviation Administration spokesman Les Dorr said on August 27.

Dorr said the move was prompted by the fire in Japan and one other incidents.

The FAA's emergency airworthiness directive, issued on August 25, applies to all 737-600, -700, -800, -900 and -900ER series planes, the first of which entered service in January 1998 with Southwest Airlines, which flies only 737s. In the United States, the planes also are used by Alaska, American, Continental, Delta and other carriers.

Slats slide out the front edge of the main wings during takeoff and landing to stabilize the aircraft, along with flaps that come out of the wings' rear edge.

On August 23, investigators in Japan found that a bolt from a right wing slat had pierced the fuel tank of the Taiwanese jetliner that caught fire after landing on the Japanese resort island of Okinawa. All 165 people aboard evacuated safely seconds before the plane exploded.

A fuel leak through that hole appeared to have caused the fire on the China Airlines Boeing 737-800, said Kazushige Daiki, chief investigator at Japan's Aircraft and Railway Accidents Investigation Commission.

The FAA ordered a detailed inspection within 24 days to be sure that the downstop assembly, which limits how far the slats can emerge from the wing, is installed properly and repaired if needed. It also ordered that the nut and bolt that hold the assembly in place be tightened to specifications. Additionally, it ordered that the process be repeated at least every 3,000 takeoff and landing cycles.

The FAA estimated the cost for the US fleet at US$62,640.

The FAA order said loose parts from one 737-800 downstop assembly had punctured the slat housing, which caused a fuel leak and fire that destroyed the plane, a clear reference to the China Airlines fire, although the company was not mentioned by name.

In the other case, a nut fell off the assembly and was pushed through the housing wall when the slats were retracted, the FAA said. Later, the operator found fuel leaking from the slat housing.

Following August 23's findings, Japan's Transport Ministry ordered three Japanese airlines that own Boeing 737-800s to inspect the leading edge slats on the main wings to ensure bolts were in place before their first flight took off on August 24, said ministry spokesman Yusuke Asakura.

Vicki Ray, a spokeswoman for Boeing Co, said the aircraft maker had received four reports of the nut coming loose from the downstop assembly and had issued a service letter in December 2005 to all operators of the newer model 737s telling them to check to be sure the nut was tightened properly. The service letter has been updated several times since, most recently last month, Ray said.