We went back through 4,000 missions to find out why flights got scrubbed. Three quarters of them traced to the same short list.
Battery temperature at launch, RTK fix quality, an unlogged obstruction, and a boundary file that did not match the ground. None of them are interesting problems. All of them cost a morning when they turn up at the field edge instead of the day before.
The checklist now runs the night before every contract day, and the abort rate has dropped by two thirds. The remaining third is weather, which no checklist has ever fixed.