The government ordered inspections Saturday of the latest generation of Boeing 737s flying worldwide to see if any have potentially defective flight control modules that could make the planes hard to control.

The Federal Aviation Administration's emergency order, which covers 737s in the 737-600 through 900 series that were produced since May 21, gives airlines 10 days to complete the review. Most of the 93 aircraft are in service, but some may be still at Boeing, FAA spokesman Paul Takemoto said.

Each plane has two modules that control hydraulic fluid to the flight control system. A failure of both modules could significantly affect a plane's flight control systems by almost jamming the controls, making the jetliner sluggish and very difficult to operate, Takemoto said.

He said the airworthiness order requires carriers to check the serial numbers before flying again and replace those with the suspect serial numbers. The FAA has no jurisdiction over foreign carriers, but they almost always follow its recommendations.

To check the modules, "You just have to look up into the wheel well and check the serial number," Takemoto said.

The FAA said it's looking for a recent batch of modules that has a high rate of failure. Fifteen modules were found to be defective, four while in flight and 11 during inspections on the ground, Takemoto said. None caused an accident, he said.

There are 84 foreign aircraft with the modules from the bad batch and nine with U.S. carriers, but Takemoto said not all have been delivered. He also said some of those already delivered may not yet be in service.

Three foreign airlines reported Saturday they already had acted on Boeing's warnings about the possibly defective parts. Australia's two main carriers, Qantas and Virgin Blue, said they had grounded eight Boeing 737-800s to exchange the parts. At least seven flights were canceled. In Ireland, the budget carrier Ryanair grounded two 737s overnight for the repairs and returned them to the fleet Saturday.

A spokesman for the company that made the modules, European-based Smiths Aerospace, had no immediate comment on the FAA order.

James McKenna, managing editor of Aviation Maintenance magazine, said the airplanes are probably built so that if all of the flight control modules break, the pilot still has some mechanical physical control of the airplane.

"Still," he said, "there's a possibility that this could lead to a crash."

Seventy-eight of the 93 aircraft with possibly faulty modules have two of the modules on them, Takemoto said.