International Consolidated Airlines (IAG), the combined business of British Airways and Spain's Iberia, is buying eight of Airbus's A330-300 aircraft with an option on another eight.The planes, due to be delivered between autumn 2012 and spring 2014, will replace up to 16 Airbus A340 family aircraft within Iberia's longhaul fleet, which currently consists of 18 A340-300 and 17 A340-600 aircraft. "The new aircraft will be more cost effective to operate as they are around 15% more fuel efficient than the aircraft that they replace," the carrier said Monday. "They also have an improved environmental performance. The aircraft can be easily assimilated into Iberia's existing longhaul fleet, reducing the need for additional crew training and maintenance costs."IAG believe the new aircraft and options give it the flexibility to determine the future size of Iberia's longhaul fleet and capacity