On-time performance: what an airline punctuality figure really measures

Start with the event being timed

Departure punctuality often compares actual off-block time with scheduled off-block time: the aircraft leaves its stand. Arrival punctuality compares arrival at the stand with the scheduled arrival, rather than the moment wheels touch the runway. A flight can leave late and still arrive within the published window because the schedule includes time for taxi and airborne variation.

ICAO

A threshold changes the headline

A common measure counts flights arriving or departing no more than 15 minutes after schedule. Other analyses use different windows or report exact-on-time departures. A percentage has little meaning without the threshold and whether early flights are included. Compare the same event, window, period and route mix before ranking two carriers.

EUROCONTROL

Ask what happened to cancelled flights

A punctuality rate over operated flights may leave cancelled services outside the denominator. That can make reliability look better than the passenger experience. Read cancellation rates beside punctuality, and distinguish a weather-heavy season from a quieter one. Average delay minutes and the share of severe delays add context that a single threshold hides.

Use the figure for the right decision

For a traveller, a route-specific arrival record and the time until the next flight can be more useful than a network average. For an airline or airport, first departures, connection banks and repeated bottlenecks reveal where recovery work matters. No punctuality metric can promise the outcome of a future individual flight.