Slots at the busiest airports are subject to a "use it or lose it" rule. Historic slot allocations are also part of what decides future slot allocations. The F

Slots at the busiest airports are subject to a "use it or lose it" rule. Historic slot allocations are also part of what decides future slot allocations. The FAA is saying that they're waiving the "use it or lose it" rule for this time/airports. If airliners feel that can consolidate enough of their passengers into larger flights without losing out on future slot allocation rounds, then this is an overall win for them (especially if they can couch the move in terms of safety and cooperation with the FAA). In a sense, part of the value of holding a slot is just denying it to your competitors (in addition to directly making revenue off of it). This waiver allows airliners to gain this portion of the value of the slots, without partaking in the risk of actually trying to generate revenue off it is (which is why exactly the use or lose it rule is usually in effect).