A flight delay's real cause is usually invisible on the airport board: most U.S. delays trace to a late-arriving aircraft — the plane flying your route is running behind from an earlier leg (about 40%, BTS). This free tool infers that cause from live data, then tells you your rights.
Live status from AeroAPI, the FAA, and NOAA · we never invent a reason.
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Status apps tell you that you're delayed. This tool infers why, by fusing four live signals into a single most-likely cause with a confidence level and the evidence behind it. Confidence is earned — it rises only when independent sources agree, and we degrade to “cause unclear” rather than guess.
The single most common real-world cause — around 40% of delayed U.S. flights, more than any other category (U.S. Bureau of Transportation Statistics). We track the specific aircraft assigned to your flight and check whether its previous leg is running behind — if your plane is still in the air somewhere else, that's usually why.
When the FAA holds departures to (or from) an airport, the National Airspace System status feed states why — weather, traffic volume, equipment, or a runway. We match that to your departure or arrival airport and read the stated reason.
We read the current METAR (aviation weather observation) at both your origin and destination for low ceilings, poor visibility, high winds, or thunderstorms — the conditions that actually ground flights.
Live status gives the scheduled vs. estimated departure and the gate. When a flight is delayed but no ground stop, late inbound aircraft, or bad weather shows up, that points to an airline-operational cause (crew or maintenance) — which we say with low confidence, never as a claim.
Sources: AeroAPI (FlightAware) for live status and inbound-aircraft tracking, the FAA National Airspace System status feed, and NOAA aviation weather (METAR). Delay-cause statistics from the U.S. Bureau of Transportation Statistics. Rights guidance from the U.S. DOT — updated August 2026.
Updated August 2026
One delay rarely stays one delay: because airlines fly the same aircraft — and rotate the same crews — across several legs a day, a flight that lands late hands its delay to the next flight, and the next, which is why a late-arriving aircraft is the most common cause of U.S. delays (~40%, BTS).
That knock-on effect has a name — reactionary delay — and it is the single biggest delay category overall (~46% of departure delay in Europe, Eurocontrol). The practical takeaway: delays compound through the day and only reset overnight, so earlier flights are the more reliable bet — and if your flight is already caught in a cascade, the fix is usually to get onto a different, healthier aircraft rather than wait it out.