Mathfox
If you look at the track record of aircraft incidents
1 - TWA 840 (1969)
2 - Dawson's Field
3 - TWA 840 (1986)
4 - 9/11
5 - Richard Reid (shoe bomber)
6 - Glasgow Airport
Then he can make his argument on the basis of facts. I am not aware of Irish terrorists ever taking action against aircraft, per the incidents cited above, so your hypothesis is disproven by historical record.
I work regularly in the middle east and have many friends who are sunni moslem, some of the best people I have had the privilege to meet.
But it is difficult to counter Espada's logic, especially in the light of recent terrible events.