Ellion
The Shannon stopover is holding up the re-negotiation of the US bilateral which severely limits the possibility of new US services - witness EI flying to BWI rather than IAD due to getting around this problem using a secondary airport.
"Airlines fly from SNN because they choose to" - if they *choose* to fly to DUB then they *must* choose to fly to SNN! Those are the terms of the stopover as currently constituted.
As previously discussed, this is also impeding Ire-Can services, e.g. DUB-YYZ as it would have to have the route DUB-SNN-YUL-YYZ!
Finally, while the cost of DUB-SNN is not that of a transatlantic, it does add cycles to the airframe, not just hours. Thus a DUB-JFK, DUB-SNN-JFK route is 25percent more cycles than DUB-JFK alone.