Aer Lingus went through a long time of being schizophrenic about the name of its transatlantic operations, which seemed to be called something different almost every year, along with various aircraft titles. My understanding was they had been advised that Aer Lingus would not be understood in the US market, so it was marketed there as Irish International. They must have had a separate AOC as the flight designator was IN instead of EI, and the Dublin-Shannon sectors were jointly designated. The fleet did seem wholly integrated, even the 720s sometimes turned up at Heathrow, and I certainly recall one arriving at Bristol, on the old shorter runway at Lulsgate, as a Viscount substitute with about 25 passengers. Various sources seem to give various dates for when the alternative name was given up; I believe it was always known colloquially among passengers and the public just as Aer Lingus.