Aerojet Rocketdyne [AJRD] said Tuesday evening that its stockholders have approved the $4.4 billion sale of the company to Lockheed Martin [LMT], clearing a hurdle on the deal that is still expected to close in the second half of 2021.

The transaction still needs federal antitrust approval.

The pending deal is getting scrutinized by the federal government. In February, Lockheed Martin said the Federal Trade Commission had requested additional information about the acquisition as part of the regulatory review.

Aerojet Rocketdyne supplies tactical rocket motors and other propulsion systems for missiles and large rockets, competing with Northrop Grumman [NOC], which entered these markets through its acquisition of the former Orbital ATK. Gregory Hayes, CEO of Raytheon Technologies Corp. [RTX], also said last month that his company has concerns about the pending acquisition, highlighting that Aerojet Rocketdyne is an important supplier of solid rocket motors to his company.

The U.S. government requires Northrop Grumman to continue supplying rocket and missile propulsion systems to other companies in the aerospace and defense industry and Lockheed Martin says it will do the same with Aerojet Rocketdyne.