The U.S. Department of Transportation said Tuesday that the states, which include California, New York and Illinois, will help ensure that government enforcement activities keep up with a current boom in air travel.

Under an agreement announced by Transportation Secretary Pete Buttigieg, state attorney general offices will be able to investigate complaints about airline service. If they believe an airline violated the law or is refusing to cooperate with investigators, the states could refer cases to the Transportation Department for enforcement.

In return, the Transportation Department, or DOT, will give the states access to its consumer-complaint system and train state employees about federal consumer laws covering airlines.

“This is a partnership that will greatly improve DOT’s capacity to hold airlines accountable and to protect passengers,” Buttigieg told reporters.

Buttigieg pointed to travelers whose flights are canceled and then must wait days for another flight or pay more to fly home on another airline. “Things like that are a violation of passenger rights, and we are seeing far too many cases of that,” he said.

Other states whose officials signed the “memorandum of understanding” with the Transportation Department are: Colorado, Connecticut, Maine, Maryland, Michigan, Nevada, New Hampshire, North Carolina, Oklahoma, Pennsylvania, Rhode Island and Wisconsin, plus the District of Columbia, the Northern Mariana Islands and the U.S. Virgin Islands.

Buttigieg, a Democrat, repeatedly cast the agreement as bipartisan, but only two of the state officials who signed on are Republicans. Buttigieg indicated his department hopes to recruit more states.

Under U.S. law, the federal government alone regulates consumer-protection laws covering airlines. The carriers are not legally required to respond to state investigations.

Consumer advocates have pushed to expand enforcement power to the states. However, both the full House and a key Senate committee declined to include that proposal in pending legislation that covers the Federal Aviation Administration, part of the Transportation Department.

“During the pandemic, we actually got more complaints about airline traffic than any other topic, and it was frustrating” because the state had no authority to investigate the complaints, Colorado Attorney General Philip Weiser said.

Weiser argued that Congress should give states power to enforce airline consumer-protection laws, “but I have to say, we didn’t wait for Congress to act.”

Consumer groups praised the agreement while saying they would rather see Congress write into law the power of states to regulate consumer-protection rules.

“This is the next best thing,” said William McGee, an aviation expert at the American Economic Liberties Project, which opposes industry consolidation. “We don’t look at this as a threat to DOT’s authority. We look at it as the states assisting DOT, which doesn’t have the staffing to handle all the complaints they get.”

Airlines for America, a trade group representing the largest U.S. carriers, said it works with state and national groups “to constantly improve the customer experience for all passengers. We appreciate the role of state attorneys general and their work on behalf of consumers, and we look forward to continue working with them.”