United Launch Services LLC has been awarded a $138 million U.S. Air Force contract modification for launch vehicle production services for the Atlas V 541 system.

The contract also covers missions specific commodities for four previously ordered missions.

The modification also adds pre-priced contract line items for the Atlas V 541 launch vehicle configuration and mission specific commodities for the previously ordered missions and does not constitute exercised options.

Work will be performed in Colorado, Alabama and Florida, and is expected to be completed by September 2018. The Space and Missile Systems Center is the contracting activity.

Atlas V rockets are single-use launch vehicles. The 541 designation signifies a nose cone of about 5 meters in diameter, four solid-rocket boosters fastened on the central common core booster, as well as one-engine Centaur upper stage.

United Launch Alliance is a joint venture of Lockheed Martin and Boeing.