Southwest Airlines has triggered the program launch of Boeing’s 737 Max 7 narrowbody by converting 30 options that it holds for the existing 737 Next Generation family into orders for the new model. The U.S. low-cost carrier expects to take first 737 Max 7 deliveries in 2019. In a deal announced Wednesday, it also has exercised options for five more Next Generation 737-800s.

According to Boeing, the 737 Max 7’s CFM International Leap-1B engines will deliver a 12-percent saving in fuel burn compared with the most efficient of today’s in-service narrowbody fleet. The 110-foot-long aircraft will also offer 400 nm more range than the existing 737-700 model.

Dallas-based Southwest now holds ordered for a total of 180 737 Max aircraft and 137 737 NGs. The 737 Max program as a whole is supported by 1,135 orders.