CHANDLER, Ariz. — When Waymo began planning a pilot project involving hundreds of self-driving vehicles, some of the company's leading executives and operations staff headed to the airport.

They weren't going on a trip, but a scouting mission. They wanted to learn how airlines performed maintenance, loaded baggage, fueled aircraft and cleaned cabins all while minimizing time at the gate.

"We got to see some of the full aircraft turnarounds and what all they do before the planes go back out," said Rikard Grunnan, head of technical fleet operations at Waymo. "There's so many different vendors. From a high level, we could see how those interactions worked from a command center, people flowing through aircraft and doing their part within a specific time frame."

Inside the company's Phoenix-area operational hub in a nondescript warehouse here, Waymo has been replicating its findings as it operates a fleet of more than 400 vehicles, dozens of which are parked in two neat rows on a recent afternoon.

First lesson: Waymo is not trying to do it alone. Since November 2017, Waymo has partnered with AutoNation, the nation's largest automotive retailer, which sends technicians to maintain and service Waymo's Chrysler Pacifica minivans. Now, both companies say their relationship is deepening.