Two other European airlines whose names end in "A" come to mind: IberiA and AlitaliA. I don't think IB served Chicago until the 1980s, so I will go with AlitaliA.
It's interesting that for many years, Chicago-Montreal was one of the few routes from the US where you could choose a Canadian airline (AC), multiple fifth freedom airlines, but no US carrier. Not until 1977 was a US carrier (AA) given rights for ORD-YUL.