Ryanair has agreed to buy a further 10 aircraft from Boeing with a list price of $1.1 billion.
The order for 10 Boeing 737 Max 200 planes is in addition to 100 aircraft Ryanair had already ordered from the manufacturer.
The airline will take delivery of the passenger jets between 2019 and 2020.
Ryanair's entire fleet is made up of various iterations of the 737 jet.
The Max 200 model can carry 197 people, 8 more than the 737-800s which Ryanair flies at present.
According to Boeing, the newer version is also more fuel efficient and quieter.
Ryanair's chief operations officer Mick Hickey said the extra capacity on the Max 200s would help it meet its stated target of carrying 200 million passengers per year by the middle of the next decade.
Ryanair now has orders placed with Boeing for 110 aircraft and has options to purchase another 100.
Separately Avolon, an aircraft leasing company with its headquarters in Ireland, said it has signed a memorandum of understanding with Boeing for 75 737 Max 8 aircraft valued at $8.4 billion.
The deal includes an option for a further 50.
Avolon chief executive Dómhnal Slattery said the order was the biggest the company had placed with Boeing to date.
