Ryanair today surprised many industry observers by opting for Boeing’s current family of aircraft, rather than the airframer’s re-engined MAX range when signing a commitment for 175 aircraft.

The carrier says it will use 75 of the 737-800s from this new order as replacements for part of its 305-strong fleet of 737s and the remaining 100 for growth. When all aircraft from this order arrive “by the end of the delivery stream in 2018,” the airline will operate a fleet of more than 400 aircraft serving more than 100 million passengers, says Ryanair.

Ryanair’s board of directors still needs to approve the deal before it becomes a firm order.

Ryanair, like many airlines currently placing narrowbody orders, was expected to include a re-engined fleet in its order, and Boeing’s 737 MAX is scheduled to enter service in 2017. However, Ryanair chose the 737-800, suggesting that the airline was seeking a quick boost to its fleet at a bargain price.

The airline notes that it “continues to evaluate the benefits of Boeing’s 737 MAX.”

Ryanair CEO Michael O’Leary, commenting on the -800s, says, “They provide Ryanair with the additional capacity to exploit substantial growth opportunities that currently exist as many of Europe’s flag carrier and smaller airlines are restructuring and reducing their short-haul operations.”