Ohh well back to WWII and the Free State. Like I said British servicemen who found themselves in the free state as a result of lets say being shot down, were fairly quickly returned to Britain and their units.
Luftwaffe pilots however were kept in the Curragh camp for the duration.
Also the RAF were allowed to use Irish airspace - the Donegal Corridor.
Oonly after 1943 when the Americans leant on the Irish government. The Curragh camp held 2 compounds until then for airmen who had crash landed in Eire.Not only were allied airmen interned until 1943 but they had to prove to the authorities in Northern Ireland that they had legitamely escaped and had not absonded when they were parolled at weekends. If they coouldn't prove they had escaped they were handed over to the Garda and returned to Curragh.
The Donegal air corridor is something I was not aware of but quite often overflying takes place during wars and if the neutral country has no air force or a small air force it can do little about it. Sometimes overflying is with agreement i.e. Iran in the first Gulf War sometimes it is turned aq blind eye to i.e. Chile in the Falklands
But in 1943 the extermination camps were not known to DeValera (as far as I know, def not public knowledge) so any chance of using that as a reason for getting the Free State into the war on the side against the Nazis doesnt exist. The war up to that point was simply yet another bloodbath between Germany and the ol' enemy Britain.
Why join in when:
there was still soreness between Britain and the Free State over past goings on
You have no real offensive/defensive forces
When joining would probably reignited a civil war
When Britain was stretched to provide its own defense, could hardly provide it for Ireland as well.
When memory of the Somme etc was still pretty clear in the collective memory.
When Hitler would have ground the country into the mud.
...
The Free State didnt have to agree to the Donegal Corridor, the RAF could have just overflew it as you say. But it was a indication of support.
http://www.independent.ie/opinion/analysis/the-icing-on-the-cake-211669.html
Never knew some of this stuff.