WASHINGTON — US regulators have given the green light to Lockheed Martin's acquisition of Sikorsky Aircraft, according to filings made Thursday with the Securities and Exchange Commission by Lockheed and Sikorsky parent company United Technologies Corp.

The filings, first reported by Reuters, signal that Lockheed's $9 billion purchase of the American helicopter maker will not be subject to a second request for information from US regulators, which could have postponed the deal's closing substantially. Instead, the deal appears to be on track to close in the 4th quarter of 2015 or the first quarter of 2016, as Lockheed had hoped when the defense giant announced the deal on July 20.

Regulators in Japan and South Korea have also reviewed the deal, the SEC filing states.

Effectively, US regulators reviewed the deal for two months, said Jeff Bialos, a partner at Sutherland Asbill & Brennan who specializes in aerospace and defense M&A and previously served as the Pentagon's deputy undersecretary of defense for industrial policy.

"That's reasonably quick for a transaction of this size and scope," he said. "It's somewhat surprising that a deal of this magnitude didn't go to a full second request."

Government regulators spent a longer period reviewing the merger between Orbital Sciences Corp. and Alliant Techsystems into what became Orbital ATK, he said.

"There are similar types of issues here, so one would have anticipated that it would have taken longer," he said.

Bialos cautioned that the speedy approval of the deal, which may still need approval from other agencies in Europe and China, does not signal a broad philosophical change toward consolidation from the DoD.

"I would not take this to be an open season on large defense mergers, especially among primes," he said. "Rather, I would take this to mean that the facts in this particular case didn't lend themselves to an anti-competitive result."

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