U.S. officials and Boeing Co. (BA) are investigating whether defective batteries from the same batch caused incidents in two 787 Dreamliners that triggered the plane's worldwide grounding, according to two people familiar with the incidents.

If that proves to be true, it could show a flaw causing the incidents was confined to a small number of 787s, rather than a systemic fault with the plane's engineering, design or manufacturing, and could speed the resumption of flights on the jet. The people, who weren't authorized to speak publicly, said the information is preliminary and investigators haven't yet ruled out other causes.

The Federal Aviation Administration, which certified the plane in 2011, ordered flights on the 787 halted until airlines can show the plane's lithium-ion batteries "are safe and in compliance," according to an agency statement yesterday. It didn't say how the carriers should accomplish that.

The FAA's move, its first in 34 years to ground an entire plane model, set off a race to find and fix whatever caused the battery-fault warning on a 787 operated by All Nippon Airways Co. (9202) and a fire on a Japan Airlines Co. jet. The two Japanese airlines yesterday parked their 24 787s, almost half the global fleet, after the battery warning forced pilots of an ANA domestic flight to make an emergency landing.

"Nobody knows what the fix is because they don't know what the problem is," John Goglia, a former member of the U.S. National Transportation Safety Board, said in an interview.

Accident investigative agencies in the U.S. and Japan, as well as the FAA, haven't said what started the fires.

Battery Flaws

The batteries were made by Kyoto, Japan-based GS Yuasa Corp. (6674), which has said the Dreamliner's faults may go beyond the batteries.

David Fuller's view It seems almost too good to be true, at least for Boeing and the reputation of US technology, if the main problem turns out to be a bad batch of imported batteries.