While Irish airspace remains open, UK airspace has closed due to the ash cloud, with flightsd from Derry affected.  Here is the most recent statement from City of Derry Airport -

The volcanic ash cloud in UK airspace has caused disruption to a number of flights operating to / from City of Derry Airport

The following flights have been diverted / cancelled:

Flight No.         Route

FR9884             Liverpool – City of Derry – Diverted to Belfast City

FR9885              City of Derry – Liverpool – Cancelled

FR611               London Stansted – City of Derry – Diverted to Belfast International

FR612               City of Derry – London Stansted – Cancelled

RE287               Dublin – City of Derry – Cancelled

RE288               City of Derry – Dublin – Cancelled