Methodology

Every flight statistic on this site is computed from the Bureau of Transportation Statistics (BTS) Reporting Carrier On-Time Performance files. BTS publishes one file a month, about two months in arrears, with one row per scheduled domestic flight by a reporting carrier. The site currently holds 36 months, August 2023 to July 2026.

From flights to totals

Each monthly file is read once. For every flight the build adds to a small set of counters for its route, its origin airport, its destination airport, its carrier, its carrier on that route, its carrier at that airport and its scheduled departure hour. Only the counters are kept. Tail numbers, flight numbers and dates are never stored, and no page describes an individual flight.

The counters are: scheduled flights; cancelled; diverted; arrived; arrived less than 15 minutes late; arrival delay in minutes (both the signed sum, where early arrivals are negative, and late minutes only); departed 15 or more minutes late; departure delay minutes; delay minutes by BTS cause category; and cancellations by BTS cancellation code.

Definitions

• On time: arrived at the gate less than 15 minutes after the scheduled arrival time. The on-time share is on-time arrivals divided by all scheduled flights, so cancelled and diverted flights count against it. This is the convention BTS uses in its own summary tables. See how BTS defines on time.
• Departed on time: left the gate less than 15 minutes after the scheduled departure time, as a share of all scheduled flights. Airport pages lead with this figure for departures.
• Average arrival delay: the mean of actual minus scheduled arrival over flights that arrived, with early arrivals negative. Tables that say "late minutes only" count an early or on-time flight as zero.
• Delay minutes per 100 flights: late arrival minutes divided by scheduled flights, times 100. A normalised total that allows a small route to be compared with a large airport.
• Delay causes: for flights that arrived 15 or more minutes late, carriers split the delay minutes across five categories. Pages show each category's share of those minutes. See delay-cause categories.
• Hour of day: the scheduled departure hour in local time at the departure airport, as filed in the carrier's reservation system.
• Route: one direction between two airports. JFK to LAX and LAX to JFK are separate routes.
• Carrier: the BTS reporting carrier, which is the company that operated the flight. A flight sold by a large airline and flown by a regional partner is counted under the regional carrier.

Periods

Headline figures cover the latest 12 months on file (August 2025 to July 2026). "Previous 12 months" means August 2024 to July 2025. Monthly charts show every month on file, with the national figure for the same month as a reference. Seasonality tables add the same calendar month across years. Month pages compare a month with the same month a year earlier.

Thresholds

• A route has a page when reporting carriers scheduled at least 120 flights on it in the latest 12 months (an average of 10 a month). Routes under 360 flights (30 a month) are built for reference but marked so that search engines leave them out.
• An airport has a page from 300 scheduled departures in 12 months and is indexed from 600. An airport-month page needs 100 departures in that month.
• An airline has a page from 1,000 flights in 12 months; an airline-month page needs 1,000 flights in that month.
• A carrier appears in a route or airport table from 24 flights, and is named in the summary text from 60.
• Rankings include airports with at least 12,000 departures and routes with at least 1,200 flights in 12 months.
• Hours are compared only when they hold at least 2 to 3 percent of the entity's flights; hours below that are drawn faded.

Limits

• Only carriers with at least 0.5 percent of domestic scheduled passenger revenue report. Smaller carriers, charters, cargo and foreign airlines are absent, as are all international flights. Airport totals are therefore lower than the airport's real traffic.
• When a carrier starts or stops reporting, airport and route totals shift for that reason alone.
• BTS occasionally revises a published month. The build keeps one aggregate per month and replaces it when a revision is known.
• Cause categories are assigned by the carriers. Weather that slows the wider system is usually filed under the National Aviation System, so the extreme-weather share understates weather's role.
• Passenger counts and load factors from the BTS T-100 series are not part of this edition: BTS offers no stable download address for those files. TSA checkpoint volumes are national only.
• The figures describe the past. They are not a forecast of any future flight and are not live status.

Text on the pages

Summaries and answers are assembled by fixed rules from the counters: the same inputs always produce the same sentence. Nothing on the site is written by a generative model.