As expected, the Department of Transporation has put restrictions on the proposed slot swap between Delta and US Airlines and LaGuardia and DC National.
Both airlines were told they can engage in slot swaps if they divest some of their current slot allocations. The DOT has requested that the airlines divest 14 pairs of slots at National and 20 at LaGuardia. Assuming the airlines aren't willing to divest additional slots then what they were planning, it reduces the overall appeal.
While both airlines are disappointed, it still lets them control the larger slice of the pie. Additionally, the biggest loser is going to be US Airways, they gain only 28 slot pairs at DCA while Delta still gains 105.
You have to wonder about the folks at US Airways who thought such an unbalanced swap was ok from the start. Sure US Airways would theoretically gain access to GRU and NRT, but is that worth such a sacrifice?