Tesla veteran Doug Field joined Apple in 2018 to lead the tech giant’s self-driving car initiative. Now, his abrupt departure to join Ford Motor Company as its chief advanced technology officer brings the future of Apple’s project into question, including the progress it has made thus far. Field is Apple’s fourth executive to lead the project in its seven-year history. Other notable manufacturers pursuing autonomous vehicles — including Tesla, Alphabet’s Waymo and Uber Technologies — have had a difficult time advancing the technology.

Bloomberg reports that Waymo also “suffered a rash of departures … and Uber Technologies agreed to sell off its autonomous-driving division last year.” After debuting the self-driving car project in 2014, by 2016 Apple was “struggling with confusing messaging from leadership, a lack of vision and problems surrounding autonomous-driving technology.”

In that year and 2019, Apple laid off hundreds of engineers. Also in 2016, Apple chief hardware engineer Bob Mansfield took charge of the effort, then known as Project Titan, and “Apple seemed to zero in on the technology that runs self-driving cars, rather than trying to build a whole car itself.” When Field, a previous Apple employee, returned in 2018, it “was seen as a sign that the company was back to building an actual vehicle.”

During his tenure, Field brought in “Tesla’s former executives in charge of self-driving software, car interior and exterior designs, and drivetrains.” With Mansfield’s retirement, Apple top AI executive John Giannandrea gained oversight of the car project. In late 2020, Apple was already attempting to make deals with car makers, “but by early 2021, it was still hard to gauge the company’s progress.”

Sources said that “development work was still at an early stage,” and top car managers Benjamin Lyon, Dave Scott and Jaime Waydo departed in the first half of 2021. Apple appointed Kevin Lynch, who ran the smartwatch and health software, to take over “some software aspects of the car” even though he didn’t come from the auto industry, and Ulrich Kranz “who oversaw panned vehicles from BMW’s electric car division and had failed stints as a top leader of Faraday Future and Canoo.”

The Wall Street Journal reports that, “Ford Motor Co. wooed Doug Field away from Apple to bolster its own efforts to better integrate software in the automobile.” “This is just a monumental moment in time — a moment in time that I think we have now to really remake a 118-year-old company,” said Ford chief executive Jim Farley. It describes Apple’s volatile autonomous vehicle project, noting that, “Apple’s rehiring of Field in 2018 sparked renewed excitement among some observers … yet Apple has remained coy about its plans.”

At Tesla, Field “worked to develop the Model 3 compact electric car that … is in many ways a supercomputer on wheels, developed from day one with software in mind.” At Ford, Farley, who “aims to expand its ability to offer digital services for which customers are willing to pay extra, which he says should generate recurring revenue,” noted that Field has “an understanding of both the tech world and automotive, where digital features and services are integrated into vehicles that must meet stringent safety and durability standards.”