Former Apple engineer Doug Field is reportedly returning to the company after five years.Peter Parks/AFP/Getty ImagesEngineer Doug Field is going back to Apple, having left Tesla in July. He worked as head of Tesla Model 3 production until his reassignment by CEO Elon Musk in April, and decided not to return to the company after a leave of absence. Field will work with Apple's Bob Mansfield, who has been leading Apple's self-driving car program, Project Titan, Reuters reports. They previously worked together when Field was vice president of Mac hardware engineering, before he left for Tesla in 2013. Neither Apple nor Tesla immediately responded to requests for comment. Apple hired Jaime Waydo, a former senior engineer with Waymo, to join its self-driving-car program in June. We took a look that what we know about the mysterious program in May, as the company grew its fleet to 55 vehicles.