The airline industry is escalating its campaign against a California law that gives pilots and flight attendants more rest and meal breaks than they are guaranteed under federal regulations.

A study commissioned by an airline trade group warns that the result will be higher costs that will force carriers to raise fares.

The trade group wants the Supreme Court to strike down the appeals court ruling which held that California-based flight crews are covered by the state's requirement that they be free from all job duties for 10 minutes every four hours.

The 9th U.S. Circuit Court of Appeals in San Francisco ruled in favor of flight attendants for Virgin America, which was bought by Alaska Airlines in 2016 and no longer exists.

The question of who gets to write labor regulations for airline workers is at the center of the dispute.

Minimum rest requirements for pilots and flight attendants are included in the Federal Aviation Administration's safety standards. The industry argues that the FAA has the power to regulate airlines.

Airline officials are afraid of being faced with a patchwork of state rules that would add complexity and cost to their operations. If the Supreme Court overturns the ruling against Virgin America, nineteen other states have rules on employee breaks and could apply them to flight crews.

The 1978 deregulation law gave the federal government sole authority over airline prices, routes and services, but not other regulations, according to lawyers for the flight attendants who sued Virgin America. There is no reason for the Supreme Court to review the appeals court's ruling.

The trade group officials said that airlines follow the rest-break requirements for ground workers.

The Biden administration's solicitor general has not made a decision on whether the Supreme Court should hear the case. The release of a report warning of dire consequences appears designed to put pressure on the administration to take the industry's side before the high court.

According to the study by InterVistas, airlines would need additional pilots and flight attendants to comply with the California law. They might use California-based flight crews more often. Depending on the approach, the changes would cost the industry between $3.5 billion and $8.5 billion a year.

It would be cheaper to close employee bases in California so that no airline flight crews are based there. It would require out-of-state flight attendants and pilots to commute to and from their flights, and it could cause more uncertainty to staffing flights in Los Angeles, San Francisco and other California cities.

The largest union of flight attendants said crew rest was just one of many issues that airlines are fighting against their employees.

Sara Nelson said that management claims they couldn't possibly keep up with state laws, but at every turn from Washington to California to New York and Illinois they were working overtime to deny aviation workers adequate nutrition, rest and sick leave.

Flight attendants need at least nine hours off before their next shift in order to be eligible for a maximum work day of 14 hours. Adding an hour of rest between shifts is proposed by the FAA. Flight crews can take meal breaks, but they have to stay on duty.

The case is before the Supreme Court.