Delta Air Lines has won a significant reprieve in its long-running fight with the US Department of Transportation over the antitrust immunity that underpins its joint venture with Aeromexico. Judges in the Eleventh Circuit Court of Appeals have vacated the DOT's order ending that immunity, describing the reasoning behind it as "arbitrary and capricious."
The dispute dates back to 2016, when the DOT granted antitrust immunity to Delta and Aeromexico for an extensive joint venture agreement. That approval allowed the two carriers to coordinate schedules closely on flights between the United States and Mexico, effectively operating parts of their cross-border networks as a single business rather than as competitors.
Why the DOT moved against the joint venture
In 2025, the Trump administration opened a review of the immunity after a dispute broke out between the US and Mexican governments over access rights at Mexico City's Benito Juarez International Airport (MEX). Washington accused the Mexican government of abusing the Open Skies agreement between the two countries by limiting slots at the capital's main gateway and pushing US carriers toward a less-used airfield on the outskirts of the city.
Mexico's position has been that slot controls at MEX were imposed because the airport is close to full capacity, and because major improvement works planned there will create further capacity constraints. The DOT nonetheless took the view that the restrictions unfavourably benefited Aeromexico, which holds the bulk of the slots at Benito Juarez. Because most travellers heading to Mexico City want to use that airport rather than an alternative, the department treated Aeromexico's position there, and by extension Delta's, as anti-competitive.
Last September the DOT issued a final order stripping the two airlines of their antitrust immunity. The following month, Delta filed suit in the US Court of Appeals for the Eleventh Circuit seeking a review of that decision.
What the court actually found
The court vacated the final order on the grounds that the market analysis used to justify it was too narrow. In previous cases the DOT had assessed the market as a whole, which here would mean every route between the United States and Mexico. For this order, however, the department focused solely on competition at MEX airport, and the court found that it had failed to explain why it departed from its own precedent.
The DOT also argued that a genuine Open Skies agreement is essential for airlines to win and keep antitrust immunity. The court noted that the United States had previously approved Japanese joint ventures despite a comparable carve-out at Tokyo Haneda Airport, which undercut that reasoning.
"We are not a rubber stamp," the Eleventh Circuit wrote, adding that "courts retain a role, and an important one, in ensuring that agencies have engaged in reasoned decisionmaking."
Not necessarily the end of the fight
Vacating the 2025 order does not permanently protect the joint venture. The DOT retains the option of issuing a fresh order to terminate the immunity, provided it addresses the shortcomings the court identified, in particular by explaining its market analysis and its departure from earlier practice. For now, though, the coordination between Delta and Aeromexico that has shaped US-Mexico air travel for the better part of a decade stays intact.
Sources: PYOK. Featured image: AI-generated by AviationShop. By Elena Vargas.
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