Ryanair had signed a purchase agreement with Boeing for 75 new 737 Max-8200 aircraft.
The move is a huge show of confidence in the 737 Max, which was recently approved for return to service by the Federal Aviation Authority in the United States.
The low-cost carrier now has a total of 210 of the planes on order, with a total value of US$22 billion.
Ryanair said it expects to take the first deliveries from early 2021, with the rest arriving over a four-year period before the end of 2024.
Boeing, chief executive, Dave Calhoun said: “Ryanair will continue to play a leading role in our industry when Europe recovers from the Covid-19 pandemic and air traffic returns to growth across the continent.
“We are gratified that Ryanair is once again placing its confidence in the Boeing 737 family and building their future fleet with this enlarged firm order.”
He added: “Boeing remains focused on safely returning the full 737 fleet to service and on delivering the backlog of airplanes to Ryanair and our other customers in the new year.
“We firmly believe in this airplane and we will continue the work to re-earn the trust of all of our customers.”
The carrier hopes to use the new aircraft to grow its low fare services into new EU countries and markets.
Ryanair and Boeing have agreed revised delivery dates, and have also agreed compensation for the direct costs incurred by the carrier over the past 18 months due to these delivery delays.
However, Ryanair said, some of this compensation has been factored into a modest reduction in the pricing of the new aircraft order.
Ryanair group chief executive, Michael O’Leary, said: “We are pleased and proud to place this enlarged order with Boeing, who have successfully completed the return to service of the Boeing Max aircraft.
“We hope to take delivery of at least 50 of these aircraft in 2021, subject to Boeing recovering its manufacturing output to deliver them.
“For as long as the Covid-19 pandemic depresses air travel, we will use these new aircraft to replace some of our older Boeing NG fleet, which will remain grounded until pre-Covid demand returns.
“But as soon as the Covid-19 virus recedes – and it will in 2021 with the rollout of multiple effective vaccines – Ryanair and our partner airports across Europe will – with these environmentally efficient aircraft - rapidly restore flights and schedules, recover lost traffic and help the nations of Europe recover their tourism industry, and get young people back to work across the cities, beaches, and ski resorts of the EU.”