The Federal Aviation Administration today finalized comprehensive training and pilot certification rules for flying air taxis, addressing a key hurdle to the deployment of electric vertical takeoff and landing aircraft.

The FAA called the rule “the final piece in the puzzle for safely introducing these aircraft in the near term.” Some flying companies hope to begin flying commercial passengers as soon as 2025.

Low-altitude urban aircraft known as eVTOLs have drawn intense global interest, with numerous companies going public like Joby Aviation and Archer Aviation. Joby shares rose 7% Tuesday, while Archer rose 3%.

“The opportunities for the use of powered lift operations are far-reaching, from transporting passengers in urban areas and short-haul operations such as air ambulance services and cargo operations to potentially serving smaller communities over time,” the FAA said.

Airlines and other companies are looking at developing transport services using battery-powered aircraft that can take off and land vertically to ferry travelers to airports or for short city trips, allowing them to beat traffic.

FAA Administrator Mike Whitaker said at a conference in Las Vegas today the rule is designed to be flexible. The regulation has “a performance-based approach, so you can look at fuel reserves and other things with this new technology, account for safety,” he said.

Former acting FAA Administrator Billy Nolen, who is chief safety officer at Archer, said the announcement is a big milestone for the deployment of flying air taxis. “Now we’ve got a roadmap,” he told Reuters.

Joby CEO JoeBen Bevirt said the rule “will ensure the U.S. continues to play a global leadership role in the development and adoption of clean flight.”

The FAA said previously that air taxi operations will begin at a low rate, similar to helicopters, and using existing routes and infrastructure such as helipads and vertiports.

The FAA said the rule allows pilots to train with a single set of flight controls while prior rules required two flight controls – for the student and instructor.

Delta Air Lines invested $60 million in Joby in a partnership aiming to offer passengers air taxi transport to and from airports in New York and Los Angeles within a few years. Earlier this month, Toyota invested $500 million in Joby.