The U.S. Transportation Department (DOT) has ordered Delta Air Lines and Aeromexico to terminate their joint venture, ruling that the partnership distorts competition in U.S.–Mexico markets.

The final order brings an end to the carriers’ nearly decade-long immunized partnership, with antitrust immunity set to end on Jan. 1, 2026.

Delta, which holds a 20% stake in Aeromexico, said it was “reviewing the department’s order and considering next steps,” calling the decision “disappointing” and warning it would cause “significant harm to U.S. jobs, communities and consumers.” The carrier emphasized that flights will continue to operate as normal in the meantime.

DOT said the decision is necessary because of “ongoing anticompetitive effects in U.S.–Mexico City markets that provide an unfair advantage to Delta and Aeromexico as two predominant competitors and create unacceptable actual and potential harm for stakeholders, including consumers.”

The agency cited a series of interventions by Mexico’s government, including slot confiscations, restrictions on all-cargo operations at Mexico City’s Benito Juarez International Airport (MEX) and successive reductions in allowable aircraft movements that DOT said were imposed without clear justification.

“In such an environment, it is inappropriate for the department to continue a grant of [antitrust immunity] because there is inadequate competition in the market,” the order stated. It added that higher fares, reduced capacity and impediments to new entrants were “not just possible, but likely.”

The U.S. and Mexico signed a new open skies agreement in 2015 committing both sides to fostering competition. However, a dispute has been ongoing since the Biden and López Obrador administrations, with DOT arguing that Mexico’s policies have distorted competition at MEX.

The Aeromexico–Delta partnership, launched in 2017, allowed the carriers to coordinate scheduling, pricing and revenue sharing across transborder routes under metal-neutral terms. OAG Schedules Analyser data for September 2025 shows the two airlines control a combined 19.9% of the market, ranking behind Volaris at 21.6%. American Airlines holds 19.3%, while United Airlines has 16.4%.

DOT stressed that its final decision does not prohibit arms-length cooperation. Delta and Aeromexico may continue codesharing, frequent flyer reciprocity and marketing agreements, and Delta is permitted to retain its equity stake.

The department also left the door open to a future reinstatement of immunity. It noted that the Mexican government has begun engaging with U.S. officials on compliance concerns related to the 2015 air transport agreement.

“If conditions improve, the department will take those improved conditions into account at that time,” the order stated. In the meantime, DOT said Delta’s equity in Aeromexico provides “a powerful economic incentive” for the partners to continue some form of cooperation subject to antitrust law.