The company says in a statement Wednesday that the order, which also includes 30 single-aisle A321ceos, is Delta's first with the European jet maker in about two decades.
A321neos have a list price of $117.4 million. The A330-300 has a list price of $239.4 million, but airlines routinely negotiate discounts.
Airbus says many of Delta's A321s are expected to be assembled at its planned assembly line in Mobile, Alabama, currently under construction with delivery scheduled to start in 2016. Deliveries of the A330s are scheduled to begin in 2015.