Au contraire! Manchester ceased 9th January 2006 so the 17,217 passengers in 2005 represents a whole year, though the attached report states that British Airways will cease the route (that Aer Arann commenced in June 2004)! Not sure what was going on. And no mention of when the Birmingham ceased.
Derry City Council - City of Derry Airport Route Update
Was it actually Loganair operating as British Airways and did they take over the Manchester route but not bother about Birmingham when Aer Arann lost the DUB PSO?
Anyway I presume that Aer Arann would want at least 20K pax p.a. on each route. Together with the Ryanair flight to Faro (also 20K) that would be 60K new passengers to make up for the 90K lost in 2009. Ho Hum.