International Airlines Group, the parent of British Airways and Iberia, has placed firm orders and options for up to 220 Airbus A320 short-haul aircraft.
As many as 120 of the aircraft are for its Barcelona-based subsidiary, Vueling.
International Airlines Group said the new aircraft would help Vueling to replace some of its existing A320 fleet and expand its business.
The aircraft are to be delivered to Vueling between 2015 and 2020, subject to approval from IAG’s shareholders.
The airlines group said the Vueling agreement includes 58 options and 62 firm orders for engines, for 30 A320ceo (classic engine option)and 32 A320neo (new engine option).
The planes ordered have a list price of about $5.4bn (£3.5bn), although IAG said it had agreed a “substantial discount”.