Delta Air Lines has been told it must leave Dallas Love Field, after months of efforts to expand at the airport long dominated by Southwest Airlines.

A letter from the director of aviation for Dallas said the city “has acknowledged that Delta cannot be accommodated at Dallas Love Field after the expiration of the current sublease with American Airlines.” Delta had been seeking to use gate space from United Airlines.

But with the city’s decision, Delta must leave Love Field by Oct. 13. Delta still flies out of Dallas/Fort Worth International Airport.

Delta said it is “disappointed that the City of Dallas has made the decision to reduce competition and travel options at Dallas Love Field by failing to accommodate our service,” and added that it will “continue to work with all parties to find a solution.”

Meanwhile, Southwest Airlines — which entered Delta territory in Atlanta through the 2011 acquisition of AirTran Airways — plans to launch nonstop Atlanta-Dallas Love Field flights Nov. 2.

Flight operations at Love Field have for years been limited because of restrictions under an unusual federal law called the Wright amendment. The restrictions end in October.