United Airlines continues to hold purchase rights to 30 Airbus A319s and A320s, as part of a deferred order for 42 dating back to the 1990s.
The order is split between 16 A319s and 14 A320s, according to the European airframer's backlog. The cancellation was first published in Airbus' orders and deliveries update for June.
Chicago-based United confirms that it cancelled 12 aircraft and says that it continually reviews its "fleet strategy and adjust our order book to fit the needs of our business" when asked why the decision to cancel the order after more than a decade.
The carrier did not list the purchase rights for the A320 family aircraft in its 2012 annual report after having done so in both 2011 and 2010.
United declines to comment further on its A320 family order.
The airline has a well documented preference for narrowbodies from Airbus competitor Boeing, since its merger with Continental Airlines in 2010. It ordered 100 Boeing 737 Max 9s and 50 737-900ERs in July 2012 and exercised nine of its options for the -900ER this past April.
United has outstanding firm orders for 89 737-900ERs and 100 737 Max 9s plus options for another 48 -900ERs and 100 Max 9s, Flightglobal's Ascend Online database shows.
The airline initially deferred delivery of the 42 A319 and A320 aircraft to 2004 or beyond in the fourth quarter of 2001 following the 11 September 2001 terrorist attacks, according to stock exchange filings. Delivery was deferred indefinitely with the right to cancel in January 2006.
United had made $91 million in pre-delivery deposits on the aircraft, according to its 2006 annual report.
The A319 and A320 order dates to United's original order for the narrowbody family in the 1990s, according to Ascend. The aircraft in question are from options exercised and new orders placed between 1998 and 2000.