Can you please advise if I have translated the following correctly:-

Control Tower = Rialú Túr
Car Rental Returns = Tuairisceáin Caranna ar Cíos
Passenger Terminal = Críochfort Paisinéirí

Your help would be greatly appreciated.

Míle Buíochas

this means "tours' control"
Control tower must be something like "túr rialaithe".
Wait for other opinions & for the 2 other questions

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Is fearr Gaeilg na Gaeltaċta ná Gaeilg ar biṫ eile
Agus is í Gaeilg Ġaoṫ Doḃair is binne

I would be surprised if any of these terms exist in the Gaeltacht. I suppose what you mean is "what Irish term has been made up by non-native speakers in Dublin for these phrases?", which is another question entirely.

In the online dictionary Focal.ie a control tower is - túr rialúcháin and a passenger terminal is - port na bpaisinéirí, or - críochfort paisinéirí.

Rialúcháin? that's weird! why not simply rialaithe? Looks like those who made up new words use suffixes at random: -án, -adán, -achán, -úchán...

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Is fearr Gaeilg na Gaeltaċta ná Gaeilg ar biṫ eile
Agus is í Gaeilg Ġaoṫ Doḃair is binne

Well that's what they give. About hiring a car as Gaeilge, here's a website I've mentioned before (but I'm not in any way responsible for the quality of the Irish they have there either)
- Citizen's Information.ie/Faisnéis do Shaoránaigh -
Gnóthaí Tomhaltóirí - Gluaisteánaíocht - Ag Tógáil Cairr nó Veain ar Cíos
(by the way, I've just looked at a few of the websites of car-hire companies in Ireland and not one of them has the option of clicking on 'Gaeilge' not even at Cork Airport. Enterprise Rent-a-car give you the options of English, Français, Español and Deutsch, and Dooley's also have a choice of five European languages but Gaeilge isn't one of them. On their website, the name of Aerfort Corcaí is both languages, but that's as far as it gets, though it is true that (on the web) I have seen signs in Irish Airports in Irish.)

The -ú ending (of a verbal noun) represents the action whereas the -án, -adán, -achán, -úchán ending represent the results of those actions:

aistriú "(the act of) translation/translating"
aistriúchán "a translation" (i.e., the written document resulting from the act of translating something)

rialú "(the act of) ruling/regulating/controlling"
rialúchán "regulation/control"

If you were "handing over control to someone" it would be rialúchán rather than rialú, I would think.

Túr rialaithe could be interpreted as "controlling tower" as opposed to túr rialúcháin "control tower". Native usage, however, might not necessarily be so logical, and they could just be interchangeable.

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Múinteoir Gaeilge - Irish Teacher
My "specialty" is Connemara Irish, particularly Cois Fhairrge dialect, but I can also speak Ulster and Munster Irish with native-level pronunciation.
Is fearr Gaeilge ḃriste ná Béarla cliste, cinnte, aċ i ḃfad níos fearr aríst í Gaeilge ḃinn ḃeo na nGaeltaċtaí.
Gaeilge Chonnacht (GC), go háraid Gaeilge Chois Fhairrge (GCF), Gaeilic Uladh (GU), Gaelainn na Mumhan (GM), agus Gaeilge an Chaighdeáin Oifigiúil (CO).

In a geographical context, it says (whatever that would be). In the appendix at the bottom it gives "túr rialaithe", as Lughaidh said, from the Dictionary of Military Terms, so I suppose that would refer to an airport control tower.

patrickjwalsh, b'fhéidir go mb'fhearr leat na comharthaí a bheith i mBéarla amháin?

That a very useful principle. But I would have said -chán was the abstract noun as well as the final result of the action - whereas -ú was the concrete activity. So you have aistriú as "the act of translation", but isn't that the abstract noun, which should be aistriúchán?

Or you could just say -ú is -ing in English and -chán is -tion?

If you say: tá fáilte roimh cheartúchán - are you welcoming [the final results of an act of correcting] or [the abstract noun of correction] (or maybe there's no difference between the two?)

I wonder if críochfort is a common word in spoken Gaeltacht usage - it looks like an incorrectly formed compound. It is truly an ugly word - and there are not many of those in Irish!

Well, I would have said tá fáilte roimh cheartúcháin "Corrections welcome" myself.

The fact that the word has a plural (see FGB) would point to it being (or at least including) the individual corrections rather than just the abstract concept of correcting something, wouldn't it?

ceartúcháin a dhéanamh ar cheacht/ar scríbhinn "to make (specific) corrections to a lesson/to a written document"
ceacht/scríbhinn a cheartú "to (more generally) correct a lesson/written document"

Of course, there is a lot of overlap (hence the confusion for second-language speakers) but the nuance is different.

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Múinteoir Gaeilge - Irish Teacher
My "specialty" is Connemara Irish, particularly Cois Fhairrge dialect, but I can also speak Ulster and Munster Irish with native-level pronunciation.
Is fearr Gaeilge ḃriste ná Béarla cliste, cinnte, aċ i ḃfad níos fearr aríst í Gaeilge ḃinn ḃeo na nGaeltaċtaí.
Gaeilge Chonnacht (GC), go háraid Gaeilge Chois Fhairrge (GCF), Gaeilic Uladh (GU), Gaelainn na Mumhan (GM), agus Gaeilge an Chaighdeáin Oifigiúil (CO).