ad1) protože už to tak je a ta FMC musí s něčím pracovat
ad 2) AIRAC (Aeronautical Information Regulation and Control)
What´s AIRAC? The worldwide aeronatical navigation data used by pilots is updated in the real world every 4 weeks. This regular rhythm is called the "AIRAC Cycle". In each case the actual cycle is marked with the year (first two numbers) and the month (last two numbers).
