Ryanair has agreed a massive $40 billion deal with Boeing that will see it purchase up to 300 new aircraft over the next decade.
150 of the 737-MAX-10 are firm orders while the remaining 150 are options.
The company claims the order is the largest ever placed by an Irish company for US manufactured goods.
"These new, fuel efficient, greener technology aircraft offer 21% more seats, burn 20% less fuel and are 50% quieter than our B737-NGs," said Michael O'Leary, CEO of Ryanair, who is in the US for the announcement.
"This order, coupled with our remaining Gamechanger deliveries, will create 10,000 new jobs for highly paid aviation professionals over the next decade, and these jobs will be located across all of Europe’s main economies where Ryanair is currently the No.1 or No.2 airline."
The new aircraft, which have 228 seats, are to be used to meet Ryanair’s increasing traffic, forecasted by the company to grow 80% and reach 300 million passengers a year by 2034.
Phased deliveries will start in 2027 and run until 2034, with half of the new purchases set to replace older aircraft in the Ryanair fleet, boosting efficiency and cutting emissions.
Nonetheless, the airline’s decision to grow its fleet at a time when the sector is coming under intense pressure to come up with credible plans to cut emissions is likely to draw criticism from environmentalists.
"We're in the race of a lifetime to get carbon pollution to zero fast enough to stave off the worst effects of climate change," said Oisin Coghlan, Chief Executive of Friends of the Earth Ireland.
"And Ryanair and the aviation industry in general are heckling from the sidelines."
"It doesn't matter how efficient these planes are. What matter is how many they are and how big the overall pollution impact will be."
"And until Ryanair has a plan to get to zero pollution aviation, they have no credibility on sustainability."
Because of its size, the deal will be subject to approval from shareholders at Ryanair’s AGM in September.
However, the airline anticipates that the capital spend will largely funded from internal resources, because of the strength of its balance sheet.
"The Boeing-Ryanair partnership is one of the most productive in commercial aviation history, enabling both companies to succeed and expand affordable travel to hundreds of millions of people," said Boeing President and CEO Dave Calhoun.
"Nearly a quarter century after our companies signed our first direct airplane purchase, this landmark deal will further strengthen our partnership," he added.
Today's deal marks a long-awaited truce between Boeing and Ryanair, after Michael O'Leary last year broke off talks and issued a barrage of criticism over pricing and delays in the arrival of previously ordered jets.
Ryanair exclusively uses Boeing 737s for its mainline fleet and is one of Boeing's largest customers with more than 600 planes in its fleet or on order, according to its website.
Analysts said all eyes would be on indications of whether Ryanair had managed to pay less per seat than earlier orders.
Ryanair is seen as keen to play up its low cost base, which underpins its signature brand of low fares, but Boeing is keen not to be seen as caving in on jet prices.
Ryanair said the deal was worth $40 billion at list prices, though experts note typical discounts run at more than 50%.
Despite Michael O'Leary's tough stance, however, industry sources have said Ryanair has lost some advantage in the negotiations as other carriers including United Airlines stepped up with significant orders for the MAX 10.
Ryanair shares rose in Dublin trade today.
Airline must switch to using sustainable fuel, says Minister
The Minister for Transport Eamon Ryan has said the deal with Boeing would only be a good thing if those aircraft and Ryanair switch to using sustainable aviation fuels by the end of their 20-plus years lifetime.
He said it is the Government's job to help them make that switch but that any investment made by the company now must look forward to a future when we are not consuming fossil fuels.
The Minister said that Ryanair has already done a lot of work towards this switch.
He said he welcomed the interest in sustainable aviation fuels that the airline has shown to date but that it needs to be scaled up so that the new planes just ordered will be operating sustainably in 20 years' time.
Additional reporting: George Lee
