The act of an aircraft having zero chance of becoming avialable to perform a trip due to a maintanance issue, crew issue or any other grounding item, then suddenly, like Moses parting the Red Sea, becoming available.
459TN will not be available to perform the 0500L deptarture out of MDW due to the wing falling off. Then at 0400L, Jesus the mechanic came down from heaven and put the wing back on and now, 459TN can complete the flight and as such, it's an Aviation Miracle!
When the majority of aircraft finish the flying for the day around the same time...generally around 1700L, and the crews write up maintanence issues. As result, many trips for the following day are put back in the uncovered file resulting in a 5 o'clock flush.
Boss, "Why do we have 12 trips for tomorrow still uncovered?"
Scheduler, " We just had 7 aircraft all finish their day and the crews wrote up their aircraft."