The Port of Oakland Board of Commissioners voted to move forward with renaming Municipal Oakland International Airport (OAK) to San Francisco Bay Oakland International Airport, setting up a potential legal confrontation with the city of San Francisco.

Despite San Francisco city attorney David Chiu’s threat to take legal action to stop the name change—citing federal trademark infringement on San Francisco International Airport (SFO)—the Port of Oakland moved forward with preliminary approval on April 11. The unanimous vote clears the way for the name to formally change if the board issues a final approval on May 9. The airport’s code would remain OAK.

If the name change is approved next month, OAK says it will work with “air carriers, other airports and local agencies to reflect the modification in airport and airline systems.” Chiu has said the city of San Francisco, which owns SFO, would have “no choice” but to take legal action against the Port if the proposed name change is approved.

The Port, which runs OAK, has said the renaming is needed because of a lack of awareness, especially outside the U.S., of OAK’s location in the Bay Area. The airport believes this makes airlines reluctant to start new routes to OAK and hesitant to stick with routes.

Chiu, SFO Director Ivar Satero and San Francisco Mayor London Breed maintain the name change would lead to considerable confusion for passengers regarding SFO and OAK, which sit just 30 mi. apart on opposite sides of San Francisco Bay. Passengers globally, especially those who do not speak English, will be confused when booking tickets—and passengers locally will get confused when transiting to the airports, they argue.

“SFO began operating in 1927, and has used the name ‘San Francisco Airport’ or ‘San Francisco International Airport’ throughout most of its history,” Chiu said in a statement. “The City [of San Francisco] has owned U.S. federal trademark registrations for the marks ‘San Francisco International Airport’ since 2012, with the first date of use in 1954, and the assigned airport code ‘SFO’ together with SFO’s logo since 2007, with the first day of use in 2000. Both registrations have achieved incontestable status under federal law.”

Port of Oakland Executive Director Danny Wan said after the vote that the name change is needed “for the economic health of the region,” adding: “Every day, hundreds of travelers drive from the East Bay to SFO, passing OAK because they can’t get the flight they need … Our renaming will make travel easier for thousands of people and help grow the local economy.”

Port Commission President Barbara Leslie said the change will “boost inbound travelers’ geographic awareness of the airport” and “make it clear that OAK is the closest major airport for 4.1 million people, three national laboratories, the top public university in the country [the University of California, Berkeley] and California’s wine country."

Chiu said in a public letter to the Port of Oakland prior to the vote that the city of San Francisco “will have no choice other than to pursue necessary legal action” if the name change went through.

Chiu has not yet spelled out his next steps in the aftermath of the Port’s affirmative vote.