The deal is for 25 737-8200 and 25 737-10 aircraft, plus 100 options.
The 737-8200, seating up to 210, was formerly known as the 737 Max before two fatal crashes that led to a software redesign. The 737-10 is a new, larger version that can seat 188-230 passengers. Both are short- to medium-range aircraft.
IAG said the aircraft would be delivered between 2023 and 2027 to be used “by any airline in the Group for fleet replacement”.
Luis Gallego, IAG chief executive, added: "The addition of new Boeing 737s is an important part of IAG´s short-haul fleet renewal.
"These latest-generation aircraft are more fuel efficient than those they will replace and in line with our commitment to achieving net-zero carbon emissions by 2050."
