Low-fares airline Ryanair has confirmed it would be buying around £10 billion-worth (11.6 billion euro) of new planes in a move that will create more than 3,000 jobs.
The no-frills Irish carrier said it would be taking 175 of Boeing's new 737-800 aircraft, which will be delivered over the period up to 2019.
First announced as a commitment in March, the now-firm order was finalised at the Paris Air Show on Wednesday.
The new planes will allow Ryanair to grow its fleet to more than 400 aircraft, serving more than 100 million passengers a year across Europe by 2019.
Ryanair chief executive Michael O'Leary said: "We are pleased to finalise this firm order, creating over 3,000 new jobs for pilots, cabin crew and engineers.
"These 175 new aeroplanes will enable us to lower costs and airfares even further."
Boeing commercial aeroplanes president and chief executive Ray Conner said: "I could not be more proud to see the partnership between Ryanair and the Boeing Company extended for the years to come."