He then found himself considering a career on Wall Street, doing something he didn’t want to do away from where he wanted to be: back in Vermont.

“There’s a brain drain” among engineers from his home state, he said. “People go away to college and come back when they’re 40, because they realize San Francisco or Boston isn’t the cat’s meow.” Returning to Burlington in his mid-20s, Mr. Clark became director of engineering at a company that designed power converters for Tesla.

In 2017 he attended a conference where Ms. Rothblatt made her pitch for an e-helicopter.

“There were like 30 people in the room, none of whom excited me,” Ms. Rothblatt recalled. “Then Kyle stood up and said, ‘I’m an electronics and power systems person, and I’m confident we can achieve your specification with a demonstration flight within one to two years.’ Other people were shaking their head. He was probably the youngest guy in the room. So I came up to him during break and said, ‘Where’s your company located?’ And he said, ‘I live in Vermont.’”

A few weeks later, after a second meeting, Mr. Clark drew a watercolor of his design and sent it to Ms. Rothblatt. Within hours, $1.5 million in seed capital for Beta Technologies had been wired to his bank account.

“He drew a nice design,” Ms. Rothblatt said.

A prototype with four tilting propellers was assembled in eight months, with Mr. Clark piloting the vehicle himself. Built in Burlington, the plane had to be flown over Lake Champlain, away from population centers.

“It was so fun to fly it that we found an excuse to every chance we could,” Mr. Clark told an audience at M.I.T. in 2019. Ultimately, though, it turned out to have too complex a design and Mr. Clark threw it out. He created a streamlined prototype modeled after the Arctic tern, a small, slow bird capable of flying uncanny distances without landing.

Since then, Beta’s work force has grown to over 350 from 30. The company’s headquarters have expanded to several buildings wrapping around the runway at Burlington International Airport, with plans for an additional 40-acre campus.