A United Launch Alliance Delta II rocket launches from Vandenberg Air Force Base, Calif., on July 2. United Launch Alliance, a joint venture of Lockheed Martin and Boeing, announced Tuesday that CEO Michael Gass will be replaced by Tory Bruno. (Bill Ingalls/NASA)

Michael Gass, who has served as the president and chief executive officer of United Launch Alliance since it was founded in 2006, is being replaced by Tory Bruno, a longtime aerospace executive, the company announced Tuesday.

The move comes as ULA, a joint venture of Lockheed Martin and Boeing, has been targeted by Elon Musk’s start-up, SpaceX, which is suing the government for the right to compete against ULA under a contract to launch defense payloads into space. Musk has said the contract, which was awarded to ULA on a sole-source basis, should be canceled and rebid.

Gass recently helped spearhead an effort to push back against the attacks, highlighting ULA’s years of successful launches over SpaceX’s relative inexperience.

“Mike’s track record speaks for itself: 86 successful launches in a row, including many of our nation’s most complex and critical space missions,” said Rick Ambrose, executive vice president of Lockheed Martin Space Systems and a ULA board member.

Bruno joins the company from Lockheed Martin, where he was vice president and general manager of Strategic and Missile Defense Systems.