Oneworld carriers British Airways and Iberia have signed their formal merger agreement, following the tentative pact they forged last November.
The merger will create a new holding company, International Airlines Group, under which both carriers will retain their operations and brands.
BA and Iberia state that they expect the merger to be completed late this year.
The terms of the agreement are "consistent" with November's binding memorandum of understanding.
BA says the new group will operate a combined fleet of 408 aircraft, covering more than 200 destinations and transporting over 58 million passengers per year.
"It has been structured so that it can take advantage of further consolidation in the global aviation industry," it adds.