Source
The U.S. Department of Transportation's Bureau of Transportation Statistics (BTS) Marketing Carrier On-Time Performance file. It lists every scheduled domestic flight by the airlines required to report, plus the regional airlines that fly for them: scheduled and actual times, delay minutes and causes, cancellations and diversions. BTS publishes each month about two months later, and we rebuild the site when it does.
Definitions
- On time: arrived less than 15 minutes after the scheduled arrival time, the official DOT definition. The rate counts all scheduled flights, so a cancelled or diverted flight counts as not on time.
- Airline is the airline that sold the ticket. A "Delta Connection" flight operated by SkyWest counts as Delta, and pages show the operator next to it.
- Hour is the scheduled departure hour, local time at the departure airport.
- Typical arrival is the median arrival time against schedule for completed flights. Negative means early. When late is the average delay of flights that arrived 15+ minutes late.
- Delay causes are reported by the airlines for flights 15+ minutes late, as minutes of delay: airline (crew, maintenance, cleaning, fueling), NAS (air traffic control, airport operations, non-extreme weather, heavy traffic), severe weather, security, and late-arriving aircraft (the inbound plane was late).
Windows
Headline figures, hours, airlines and day-of-week cover the trailing 12 months. Month-of-year charts pool every calendar month across the full window (2023–2026), so seasonal patterns aren't one year's luck.
Minimum samples
- No percentage is shown from fewer than 100 scheduled flights. A smaller cell shows "—". At 100 flights a rate of 80% is accurate to about ±8 points. One exception: a single flight number's month-by-month and day-of-week charts use smaller groups (as few as 15 flights) because one flight a day can't reach 100 in a month; those bars are rough, and the hover text shows the count.
- A route gets a page with at least 365 flights in the past year (about one a day). An airport needs 1,000 departures.
- A flight number gets a page with at least 120 flights on the same airline, number and route in the past year, and 20+ in the latest three months, so it's still flying. Flight pages show a "likely range" (95% interval).
Caveats
- Domestic flights only, and only the airlines that report to DOT and their regional partners. Small carriers and international flights are not included.
- Past performance is a guide, not a forecast. A storm or an outage on your travel day matters more than any average.
- Flight numbers move between routes and times. We key every figure on airline + number + route.
- This is not live status. For where your plane is right now, check your airline, the FAA or a flight tracker.
- Connection-risk numbers are estimates from past arrival delays of flights that landed, and assume your onward flight leaves on time. Cancelled and diverted inbound flights are reported separately: on one booking the airline rebooks you.