What an AIRAC cycle means for you

Why aeronautical data changes every 28 days, how the cycle numbering works, and how to make sure your charts are never out of date.

One calendar for the whole world

AIRAC, Aeronautical Information Regulation and Control, is the schedule that keeps aeronautical data in step worldwide. Rather than changing procedures whenever they are ready, states publish them on fixed dates, every 28 days, all using the same calendar.

That is why an airway, a frequency or an approach plate changes overnight for everyone at once.

Reading the cycle number

A cycle is written as two digits of the year and the cycle number within it: 2605 is the fifth cycle of 2026. There are thirteen in most years, and each one takes effect at 0000 UTC on its effective date and runs for exactly 28 days.

What it means in the cockpit

Your navigation database, your charts and your tablet apps all carry a cycle. Flying with an expired one means flying with data that may no longer match what the controller and the chart in front of them say.

The practical risk is small on a local flight and very real on an IFR route you have not flown for a month.

Never being caught out

caeloo tracks the current cycle, shows when the next one takes effect, and can remind you in the days beforehand so your database update happens on the ground rather than at the holding point.