(Bloomberg) -- Delta Air Lines Inc. is prepared for a lengthy battle over the US government’s planned suspension of its transborder partnership with Grupo Aeromexico SAB, which regulators have said should wind down by October. 

The proposed breakup of the relationship has set the two carriers at odds with the US Transportation Department, saying the plan punishes the partnership for Mexican government actions beyond their control. 

“It will be a long, drawn-out process,” Delta Chief Executive Officer Ed Bastian said in an interview. “We have a lot of parties engaged at this stage, and a lot of customers are engaged and very upset.”

The agency cited the effect on American carriers of Mexico’s decision to prohibit cargo operations at Benito Juarez International Airport, the main airport serving Mexico City, due to traffic saturation levels. 

While the Mexican government has not offered plans to add operational capacity at Benito Juarez, President Andres Manuel Lopez Obrador has been trying to boost traffic at Felipe Angeles International Airport, a flagship project 50 kilometers (31 miles) north of Mexico City.

The DOT action follows US suspension last year of a joint venture between ultra-low-cost carriers Allegiant Travel Co. and Mexican airline Grupo Viva Aerobus SA over concerns Mexico wasn’t meeting requirements in a transport agreement between the two nations.

Read more: Delta Urges US to Drop Plans to End Aeromexico Partnership

Termination of the Delta-Aeromexico partnership, which the DOT has called to wind down by Oct. 26, could harm consumers by forcing cancellation or reduction of some routes and slowing economic growth in Mexico, Delta has said. Antitrust protection under the agreement allows the carriers to jointly plan flights, routes and pricing.

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