Uber will be ready to start commercial service with urban air taxis by 2023, Mark Moore, Uber Elevate’s engineering director, said at the Elevate Summit on Tuesday. The electric-powered VTOLs are still in development, but Uber released its latest concept showing a four-passenger aircraft with four rotors. “Stacked co-rotating rotors or propellers have two rotor systems placed on top of each other rotating in the same direction,” Uber says. “Initial experimentation of this concept has revealed the potential for significantly quieter performance than traditional paired rotors and improved overall performance.” The company said testing will begin in 2020, with Dallas-Fort Worth and Los Angeles as the first test sites. Their goal is to provide the service at a rate comparable to an Uber ride on the ground.