What Causes Flight Delays?
Breakdown of delayed flights across the US (2019-2025)
Delay Causes Distribution
Carrier Delay
35.8%Delays caused by the airline itself — maintenance, crew problems, aircraft cleaning, baggage loading, fueling, etc.
Weather Delay
5.9%Delays caused by significant meteorological conditions — thunderstorms, snow, fog, wind, or other extreme weather.
National Aviation System (NAS)
19.7%Delays attributable to the national aviation system — air traffic control, airport operations, heavy traffic volume.
Security Delay
0.2%Delays caused by evacuation of a terminal, re-boarding due to security breach, inoperative screening equipment.
Late Aircraft Delay
38.4%Delays caused by a previous flight arriving late, causing the current flight to depart late (cascading effect).
Data source: Bureau of Transportation Statistics (BTS) On-Time Performance dataset. Statistics are based on reported flight data from 2019-2025. See our data methodology for details.