Found this interesting documentation of the first 15 routes Ryanair served (i.e. up to November 1989):
https://www.routesonline.com/news/29...the-beginning/
It says that Galway - Luton was at one point served with the leased-in Partnair Convair 580 as a step-gap measure before the arrival of the ATR42s:
https://www.airliners.net/photo/Ryan...ir-580/1269944