There isn't actually much of a gap at all. Although, Shannon appears to have around 600K passengers more, that figure includes Dublin-North America passengers who never leave the aircraft. Even though Shannon has done a good job of retaining services in the Open Skies era so far, the one thing we can say is that there will be a massive fall off in this number of transit passengers. Other than a statistical change, it will have little effect on Shannon as there is no charge for these passengers and they don't spend in the airport. There will be a small loss of revenue because of fewer aircraft movement, but other than pride, the loss is negligible.