The AIRAC cycle was adopted by ICAO in 1964 and further improved over the years. Key are the worldwide effective dates with 28 days intervals (e.g. 4 August 2005, 1 September 2005, 29 September 2005, ...). Effective days are always on a Thursday.
It may look indeed like a long period, 28 days, or even 56, but it should be understood that aeronautical information changes (mostly published through so called AIRAC Amendments) require:
- Changes to local systems which includes interpreting, re-typing and re-coding the information.
- Verification and Correction as publications are unfortunately seldom perfect.
- Validation against other data; Flight Plans are just one example.
- Re-distribution, hereby think of Charts and Flight Management Systems to a fleet which can be anywhere in the world.