American Airlines Group Inc. and JetBlue Airways Corp. must dissolve a partnership covering flights across the northeastern US after a federal judge agreed with antitrust enforcers that the alliance would reduce competition and boost fares for consumers.

“Though the defendants claim their bigger-is-better collaboration will benefit the flying public, they produced minimal objectively credible proof to support that claim,” US District Court Judge Leo Sorokin said in a ruling Friday. “Whatever the benefits to American and JetBlue of becoming more powerful — in the northeast generally or in their shared rivalry with Delta — such benefits arise from a naked agreement not to compete with one another.”

The decision hands a win to the Justice Department, which argued the Northeast Alliance, formed in 2020, gives the carriers too much control over competition in Boston and New York City and has led to higher prices for consumers. The airlines have the option to appeal.

--With assistance from Zoe Tillman.