Boeing Co has been awarded a USD 2.1 billion U.S. defense contract for 15 KC-46 aerial refueling aircraft. The new agreement is in addition to the initial USD 4.2 billion contract awarded by the Air Force to develop and test the aircraft, and an earlier USD 2.8 billion award for 19 planes. Boeing expects to build a substantial business from the tanker, which is based on its twin-aisle 767 commercial jet. Boeing plans to deliver 179 tankers to the U.S. Air Force and expects to sell about 400 in total worldwide. The fixed-cost contract has incurred about USD 2.4 billion in cost over runs, including a USD 201 million after-tax charge. Boeing expects to deliver the first tankers to the Air Force in late 2017.