* Southwest biggest global customer for 737 MAX - Boeing
* Airline converted options to firm orders
* Jets to be delivered from 2019 to 2022 (Adds Boeing comment)
April 27 (Reuters) - U.S. carrier Southwest Airlines has ordered 40 Boeing Co 737 MAX jets worth $4.68 billion at list price to help modernise its fleet, the airline said, making it the planemaker's largest global customer for the updated narrowbody.
Southwest converted options it held over the MAX 8 jets into firm orders, with 10 to be delivered each year from 2019 to 2022, the airline said in a statement on Thursday that announced its first-quarter earnings.
"This is first and foremost an extension of our fleet modernisation strategy," Southwest Chief Executive Officer Gary Kelly told analysts on a post-earnings conference call, according to a transcript.
"We have a very strong business case to replace older 737-700 aircraft given the superior operating economics of the MAX 8."
Southwest is the world's largest operator of 737 jets, with more than 700 of the airplanes. The airline has now ordered nearly 300 Boeing MAX jets, the most of any customer, a Boeing spokesman said. The MAX series is more fuel efficient than previous models.
Southwest warned on Thursday that the consequences of a mid-air engine explosion on a 737-700 last week will weigh on second-quarter bookings, as investigators probe the events that led to the first passenger death in the airline's history.
The carrier posted a first-quarter profit of $438 million, excluding special items, up from $372 million a year earlier. (Reporting by Jamie Freed in Singapore and Tim Hepher in Paris; Editing by Neil Fullick and Muralikumar Anantharaman)