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). Most companies have a 15% safety margin for in-flight landing distance assessments, which is also implemented in Airbus performance software.