Boeings 737 MAX-9 planned to fly for first time in April 2017

Boeing's new 737 MAX-9 is pictured under construction at their production facility in Renton, Washington, U.S., February 13, 2017. REUTERS/Jason Redmond

Boeing Co said on Tuesday it plans to fly its new 737 MAX-9 aircraft for the first time in April, a further sign the company will start delivering the large version of the workhorse plane in 2018.

Delivery of the single-aisle 737 MAX models, which replace the current 737 “NG” introduced in 1997, is crucial for Boeing to hit the financial targets it has promised investors and to offset slowing output of some of its largest jets such as the 777 and 747. Airlines want the MAX because it burns significantly less fuel than current models.

The world’s largest plane maker is creating up to five MAX versions, while planning to increase output to 57 planes a month in 2019, from 42 a month at present.

The first MAX model in production, known as the MAX-8, is on track to reach customers by mid-year.

“We are anticipating our certification of the airplane within a matter of days-weeks,” Keith Leverkuhn, 737 general manager, said at a Monday briefing embargoed until Tuesday.

The stamp of approval by the U.S. Federal Aviation Administration would come about a year after the MAX-8’s first flight and allow Boeing to begin delivering the $110 million, 162-seat jetliner in the second quarter, he said.

Deliveries trigger the bulk of airline payments. Norwegian Air Shuttle will be one of the first airlines to fly the plane commercially, likely ahead of launch customer Southwest Airlines Co, which was first to order the MAX but is taking longer to put it into service.