Just to highlight the utter stupidity of this rule - when Aer Lingus was operating to Orlando last year, they were allowed to go direct Dublin - Orlando, but on the return leg they had to make a mandatory stop in Shannon. This stop is for no reason than to satisfy the Shannon Lobby group and other local vested interests. Since the flight was inaugurated and sold as a CHARTER service (because of US restrictions which prevent Ireland flying to more than 4 SCHEDULED destinations) the passengers were ALL solely travelling between Dublin and Orlando.
You therefore had the idiotic scenario where these long range A330's, with only 10 minutes flight time remaining direct to Dublin, would have to divert off track and land in Shannon - taxi in, shut down, open doors and get a piece of paper, then close up and head off to Dublin again. No passengers on/off the flight in Shannon!
A crazy waste of fuel, crew duty time, peoples patience, aircraft maintenance cycles, landing fees etc etc etc...Irish politics at its most cynical.