lowcostportugal.net today reports that it appears that Ryanair.com are reducing the frequency on a number of routes from Porto Airport in its summer 2014 schedule:
This may be owing to a reduction of aircraft availability pending new fleet deliveries in 2015, and increase in landing fees or may reflect the opening of Ryanair's Lisbon base.
In any event, it is a warning to airport not to become to dependent on any one airline and to continue chasing new traffic:
Article (in Portuguese) here:
Ryanair corta frequências no aeroporto do Porto em 2014