The first jet airliner was, IIRC, EI-ANE of Aer Lingus. Certainly involved Leeds United and I thought their success in the Inter City Fairs Cup. Airport handbooks in the late sixties early seventies had a picture of Don Revie disembarking, possibly via the rear airstair.
I think EI were also first regular scheduled jet service with either 1-11 or 737 200 though others may have been before subbing for the regular prop types.
By 74 they were certainly only regular jet operator and that remained position until Britannia introduced IT flights to Med using Advanced 737s. Around 74/5 the Lingus flights were often operated by part cargo 737-204QC kit (EI-ASC/D) with cargo pallets being interchanged - though it was never clear what they contained