A former Tesla exec has joined a startup that's building a 350-mile electric bus

A former Tesla executive responsible for building its cars has joined Proterra, an all-electric bus start-up that's making serious moves in the industry.

Josh Ensign, Tesla's former vice president of manufacturing, left the electric car maker in May following production delays and problems with the Model X. The SUV first suffered delays relating to the design of its falcon-wing doors and second-row seats, and much of early Model X production was voluntarily recalled this year when a seat malfunction was discovered.

Ensign was one of five Tesla vice presidents to leave the company in 2016.

Ensign has now joined Proterra as chief operating officer, the start-up announced in a press release Wednesday.

Proterra unveiled a new design for its all-electric bus in early September that allows it to operate a route for an entire 18 hours - the same as a diesel bus.

Proterra's Catalyst E2 is 40-foot long bus with a range of 350 miles under typical test track conditions. To get that kind of range, Proterra worked on improving its battery tech and designing a bus that can accommodate the extra weight put on batteries for two-and-a-half years.

The Proterra bus will be fully functional soon, with the first deliveries arriving in Foothill Transit in California in early 2017.

Tesla CEO Elon Musk announced his intention of building an all-electric bus in his "Master Plan, Part Deux" in July.

Musk said he wants to make the bus smaller than current models and increase the number of passengers on it by removing the "center aisle and putting seats where there are currently entryways."

"It would also take people all the way to their destination. Fixed summon buttons at existing bus stops would serve those who don't have a phone," Musk wrote at the time.

Matt Horton, Proterra's vice president of sales, told Business Insider in a September interview that the start-up won't compete directly with Tesla because Musk is focused on lighter vehicles than heavy duty buses.

"We did certainly pay attention when Elon tweeted out his Master Plan, the thing that I think was quite clear is when you look at what they've actually proposed they are focusing on using a light duty vehicle chassis," Horton said at the time. "It's a completely different type of product they are talking about."

"I personally don't have any concerns about Tesla shifting gears," he continued.