Delta Air Lines (DAL) may lose a key part of its partnership with Aeromexico as the US government plans to take action against Mexico for breaching the 2015 US-Mexico Air Transport Agreement, the US Department of Transportation said Saturday.

The agency said it would propose revoking antitrust immunity for the Delta-Aeromexico joint venture, stopping the parties from coordinating on pricing, flight schedules, and revenue sharing.

Even if the immunity is removed, Delta would still be allowed to keep its investment in Aeromexico and maintain some aspects of the partnership, the department said.

The action is part of a broader response to Mexico's decision to cut flight slots and force cargo airlines to move out of Mexico City's main airport, citing congestion issues, the Department of Transportation said.

Delta and Aeromexico did not immediately respond to MT Newswires' requests for comment.