Originally Posted by
FlyingStone
To be able to dispatch an aircraft, it needs to be able to land within 60% of LDA at destination and alternate(s) at the estimated landing mass.
Once you are inflight, dispatch conditions are not applicable anymore and the only requirement is that LDA is greater or equal to ALD (actual landing distance for the given conditions).
From a planning point of view if runway length is limited at destination, it may this be required to (fuel) plan to fly to an alternate with a longer runway and take that plus satisfy all legalities of diversion fuels from there onwards if higher then destination requirements, as landing cannot be assumed at planning stage at destination. Think of it as planning for two alternates.