Lockheed Martin Corp said on Thursday that U.S. officials have approved its $9 billion takeover of Black Hawk helicopter maker Sikorsky Aircraft from United Technologies Corp. In a filing with the U.S. Securities and Exchange Commission, the company said authorities in Japan and South Korea had also approved the deal, but it was waiting for other regulatory approvals. Multiple sources familiar with the matter said Lockheed was now likely to close the acquisition well before the end of the year, as initially expected.