The Federal Aviation Administration has approved Boeing’s certification plan to make its troubled 787 Dreamliner batteries safe.

The move, which the government regulator announced Tuesday afternoon, allows Boeing to perform flight tests on two planes with the battery fix in place and represents a significant step toward getting the high-profile passenger jets back in the air.

“This comprehensive series of tests will show us whether the proposed battery improvements will work as designed,” U.S. Transportation Secretary Ray LaHood said in a statement. “We won’t allow the plane to return to service unless we’re satisfied that the new design ensures the safety of the aircraft and its passengers.”

Boeing CEO Jim McNerney said safety is Boeing’s top priority and that teams have been working “around the clock” to solve the battery mystery.

“Today’s approval from the FAA is a critical and welcome milestone toward getting the fleet flying again and continuing to deliver on the promise of the 787,” he said.

The FAA grounded the 787, which is made in North Charleston and Everett, Wash., on Jan. 16 after a pair of overheating incidents involving the plane’s lithium-ion batteries.

Though the root cause of the malfunctions has not been determined, Boeing submitted to the FAA what it’s called a comprehensive and permanent solution on Feb. 22.

The fix involves “a redesign of the internal battery components to minimize initiation of a short circuit within the battery, better insulation of the cells and the addition of a new containment and venting system,” according to today’s FAA statement.

The FAA noted its airworthiness directive from January, which required operators to temporarily cease 787 operations, is still in effect, and that its comprehensive review of the 787 program, announced days before the grounding in January, will continue.

Boeing had delivered 50 787 Dreamliners, including four made in North Charleston, when the battery incidents first on the ground in Boston and then in the air over Japan led to a global grounding.

Check back for more details later.

Reach Brendan Kearney at 937-5906 and follow him on Twitter at @kearney_brendan.