Delta and US Airways have until 2 July to weigh on the FAA's decision to grant their proposed slot swap only if they agree to divest 34 slots through a blind sale.
On 4 May the government denied a proposal by Delta and US Airways to divest 12%, or roughly 20, of the slot pairs in their proposed deal to AirTran, JetBlue, Spirit and WestJet.
Through an agreement unveiled in August of last year, US Airways agreed to transfer 125 Express slot pairs at New York's LaGuardia airport to Delta, while Delta agreed to give US Airways 42 slot pairs at Washington National Airport.
Shortly after US regulators handed down their final decision, Delta and US Airways said they would appeal the government's ruling in the US Court of Appeals.
A spokesman for Delta confirms that FAA has extended the time for the carriers to respond to the government's final decision by roughly a month.
US Airways CEO Doug Parker recently described the FAA's decision to require the relinquishment of 34 slots as "stunning", and warned of a lengthy appeal process.