Knock-on flight delays stem from tight aircraft and crew hand-offs, not individual flights

Analysis of European and US aviation data shows that a large share of flight delays are knock-on effects rather than primary problems. Because airlines reuse the same aircraft and crews across several legs a day, delays spread along dependencies between flights. The author argues that slack should be modeled on the gap between consecutive flights rather than on individual flights, and proposes a graph database approach in which delay propagation is computed through traversal. Referencing India's regulator findings on IndiGo's December 2025 disruption, the piece notes that maximized crew utilization left little buffer to absorb delays. The approach allows a delay to be explained as an explicit path of linked flights and slack values.