CHARLOTTE, N.C. ( TheStreet) -- At the heart of the deal enabling the merger between US Airways ( LCC) and American ( AAMRQ) is divestiture of 52 slot pairs at Washington Reagan National Airport and 17 slot pairs at LaGuardia. In a joint press release Tuesday, the two airlines said they had settled with the Justice Department and attorneys general from seven states and the District of Columbia, who had sued to block their planned merger. The carriers now expect to complete the merger in December. The carriers said they had reached agreement with the Transportation Department to divest the slots at National and LaGuardia, as well as gates and facilities to support the slots. The airlines will also divest two gates and support facilities at each of five additional airports: Boston Logan; Chicago O'Hare, Dallas Love Field and LAX and Miami International. The divestitures mean the combined company will operate 44 fewer daily departures at National and 12 fewer daily departures at LaGuardia. Currently, the companies combined operate 290 daily departures at National and 175 daily departures at LaGuardia. "To ensure much of the service currently operated by the carriers to small- and medium-sized markets from DCA is maintained, the new American has agreed with the DOT to use all of its DCA commuter slot pairs for service to these communities," the carriers said. "The new American intends to announce the service changes that will result from the divestitures in advance of the sale of the DCA and LGA slots, so that the airlines acquiring those slots have the opportunity to maintain service to those impacted communities." The carriers said divestitures will occur through a DOJ approved process following completion of the merger. They said that despite divestitures, "the new American is still expected to generate more than $1 billion in annual net synergies beginning in 2015, as was estimated when the merger was announced in February."