Aah, OLD ha ha.

The airlines must have been pushing Airbus/Boeing for the newer engines. I believe Airbus initially didn’t want to do it. It is interesting that they still over the A320OEO 😉 alongside the A320NEO. Personally, I think the A321 was the driver as a true transcontinental replacement for the B757-200. Thomas Cook followed with an order for the A321NEO, so perhaps we might see Monarch place an order, though they seem to like their A321s at the moment.