Southwest Airlines on Wednesday became the first airline to order Boeing\'s new 737 MAX 7 airplane, the smallest model of the new fuel-efficient MAX family, the companies announced. The Dallas, Texas-based carrier changed its existing order for 30 Boeing Next-Generation 737s to 30 737 MAX 7s, they said in a statement. The first delivery is set for 2019. The 737 MAX is a re-engined version of the single-aisle 737, the best-selling plane in aviation history. \"The 737 MAX 7 builds on the strengths of today\'s Next-Generation 737-700, incorporating the latest CFM International LEAP-1B engines... expected to reduce fuel burn and CO2 emissions by an additional 12 percent over today\'s most fuel-efficient single-aisle airplane,\" said Gary Kelly, Southwest\'s chairman, president and chief executive. The 737 MAX 7 will have a longer range than the current 737-700, by about 741 kilometers (460 miles). Southwest is one of the largest US carriers with an all-Boeing fleet of 694 aircraft, most of them some version of the 737. The companies also announced that Southwest had exercised options to add five more Next-Generation 737-800s to its fleet. Including the latest actions, Southwest has unfilled orders for 180 737 MAX airplanes and 137 Next-Generation 737s. Boeing said that it now has 1,315 orders for the 737 MAX family of aircraft -- the MAX 7 (126 seats), MAX 8 (162 seats) and MAX 9 (180 seats).