2 Min Read FILE PHOTO: A RAF Lockheed Martin F-35B fighter jet taxis along a runway after landing at the Royal International Air Tattoo at Fairford, Britain July 8, 2016. REUTERS/Peter Nicholls WASHINGTON (Reuters) - Antitrust regulators will likely lengthen their investigation into Lockheed Martin Corp’s proposed purchase of rocket maker Aerojet Rocketdyne Holdings Inc, industry executives said, since the deal would give the No. 1 defense contractor ownership of a vital piece of the U.S. missile industry. The $4.4 billion dollar deal, announced late last year, has raised eyebrows because Lockheed would take over a company that produces 70% of the solid fuel rocket motors and other propulsion products used in everything from antiballistic missiles, to air-to-air missiles.