Most delayed airports, September 2023

How we calculate this

Which flights count

Every flight in Airportia's schedule data (from the Aviation Edge feed) that was scheduled to depart in the period, counted once: code-share listings of the same flight are left out. Days are UTC calendar days.

Departure delay

The actual departure time (or the latest reported estimate when no actual time came in) minus the scheduled departure time. A flight that left early or on time counts as 0 minutes. A flight with no reported departure time, cancelled flights included, also counts as 0, so where the feed is patchy the average is lower than the real one.

Average departure delay

The mean of those delays over all counted flights in the period. It is not the share of flights more than 15 minutes late (the usual on-time measure), and it is about departures, not arrivals.

Why there is no "most punctual" ranking

Because flights without a reported departure time count as 0 minutes, a low average can mean missing data rather than punctuality, and the stored figures do not say how many flights had a reported time. So we only rank the most delayed, and the delay rankings leave out every airport, airline or country whose average delay is exactly 0, which almost always means that no times were reported.

Cancellations

Flights with the status Cancelled, as a share of the counted flights in the period.

Airports

Delays and cancellations are about departures from the airport. The busiest-airports ranking adds arrivals, counted on the day the flight was scheduled to depart. Totals include all tracked flights, including cargo.

Period

A month combines three 10-day periods: days 1–10, 11–20 and the last ten days of the month, weighted by departures. In a 31-day month day 21 is not included; in February the second and third periods overlap by a day or two.

Minimum sample

Only airports with at least 1,500 departures in the period (50 a day) are ranked, so a handful of flights cannot top the list. 2,823 smaller airports were left out. 976 airports with an average delay of exactly 0 were left out too: that almost always means no departure times were reported.

Coverage follows the schedule feed: some regional airports and airlines are missing or report few actual times. These are Airportia's own figures, not official statistics from airports, airlines or regulators.