SAN FRANCISCO (MarketWatch) -- The Federal Aviation Administration approved on Tuesday Boeing Co.'s BA, +2.42% certification plan which paves the way to begin testing a redesigned battery system for the company's 787 Dreamliner aircraft. The move follows a review of Boeing's proposed modifications to the faulty battery system. It is the first of several steps needed to secure FAA approval to resume flying the 787s. The jets were grounded in January following non-fatal fires aboard Japanese-owned Dreamliners. "This comprehensive series of tests will show us whether the proposed battery improvements will work as designed," 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 shares were up 0.5% at $84.56 in after-hours trade.