* Ryanair has now bought 135 737 MAX planes
* Retains 75 options
* First deliveries due in spring 2019 (Adds details of order; background)
By Conor Humphries
DUBLIN, April 24 (Reuters) - Ryanair has agreed to buy a further 25 Boeing 737 MAX planes, worth $3 billion at list prices, lifting its order of the U.S. planemaker's flagship short-haul plane model to 135, the two companies said on Tuesday.
The Irish low-cost carrier, which is the largest operator of Boeing planes in Europe, purchased 100 737 MAX planes in 2014 and took out options on 100 more.
Ryanair said the order leaves it with 75 more options.
It purchased 10 additional MAX planes in June last year, which were on top of the 2014 order.
Chief Executive Michael O'Leary in March said he expected to exercise "pretty much all" of its options.
Ryanair has dubbed the MAX a "game changer" for its business, due to a fuel consumption improvement it says could be up to 16 percent and a greater number of seats.
The configuration Ryanair has ordered has 197 seats compared to 189 in its current fleet of 737s.
Ryanair rivals easyJet and Wizz have ordered Airbus A321 planes, which seat up to 239 passengers.
Ryanair has held talks with Boeing about its new larger version of the 737 airliner, the MAX 10, which can carry up to 230 passengers, but has made clear it would only be interested if the price is lowered.
The first of Ryanair's 737 MAX planes are due for delivery in the first half of 2019 and will use CFM Leap-1B engines.
Ryanair, which currently operates around 430 Boeing 737 planes, says the MAX order will allow it reach its target of carrying 200 million passengers per year by 2024. (Reporting by Conor Humphries; editing by Jason Neely and Adrian Croft)