Volkswagen will fire three top executives on Friday, a source said. The research and development chiefs of Audi and Porsche, Ulrich Hackenberg and Wolfgang Hatz, will be removed by the supervisory board, as will VW's top executive in the United States, Michael Horn, the source told Reuters. Hackenberg and Hatz had both held senior posts at VW in development, including of engines, before they switched to Audi and Porsche. They are among VW's highest-ranking engineers.