Complex calculations are contained in the determination published yesterday by the aviation regulator, Mr Bill Prasifka. But the message is clear. Landing fees will fall next month to an average £4.41 per passenger from £4.65 at Dublin airport. In Cork and Shannon, the average fees that Aer Rianta can charge, if it chooses to, will rise to £5.29 per person from £4.65.

The "x-factor" which will reduce the rates from September 2002 is derived thus: the charge in Dublin decreases by the annual rate of inflation less 7 percentage points; in Cork and Shannon the charge decreases by the inflation rate less 5 percentage points.