US authorities have approved Lockheed Martin’s acquisition of Sikorsky Aircraft from United Technologies for $9bn cash.

Lockheed expects to close the deal by the end of this year or early next year.

The deal has gained approvals from authorities in Japan and South Korea, but is awaiting additional regulatory permits, such as from China and the European Union, where one or both the companies have business operations.

US agencies involved in the review of the deal include US Justice Department, the Pentagon, and other federal agencies.

Following completion of the deal, the company plans to integrate Sikorsky into its mission systems and training operation with a combined revenue of about $15bn a year.

"The company plans to integrate Sikorsky into its mission systems and training operation with a combined revenue of about $15bn a year."

The acquisition would open key foreign markets for Lockheed, which has an annual revenue of $45bn.

Lockheed is considering selling or spinning-off its $6bn information systems and government services business.

This would be the biggest acquisition for the company since 1996, when it acquired Loral Corp’s defence electronics business for $9.1bn, Reuters reported.

United Technologies announced the sale of its Black Hawk helicopter-maker Sikorsky to Lockheed in July this year.

United Technologies president and CEO Gregory Hayes said at the time: "We are very pleased to announce this transaction.

"Exiting the helicopter business will allow UTC to better focus on providing high-technology systems and services to the aerospace and building industries, and to deliver improved and sustained value to our customers and shareowners.

"Sikorsky’s acquisition by Lockheed Martin, one of the world’s leading aerospace and defense companies, will ensure it remains a technology leader at the forefront of vertical lift."