U.S. carrier Southwest Airlines announced Tuesday it will be the launch customer for Boeing\'s new MAX airplane, with an order for 150 of the new jets. The carrier said it also ordered 58 additional 737-700s and 737-800s, with the total order worth 19 billion U.S. dollars at list prices.Te order is the largest in Boeing\'s history, in terms of both dollar value at list price and the number of aircraft, Boeing said. The 737 MAX is scheduled for delivery to Southwest in 2017. The new LEAP-1B-powered aircraft is designed to burn 10 percent to 12 percent less fuel than the current 737. Boeing said Southwest is the first customer to finalize an order for the 737 Max. Including this order, Boeing now has orders or commitments from 13 customers for more than 900 of the new model. The 737 MAX is Boeing\'s response to rival Airbus\' 320neo, which also uses new engines for fuel-efficiency. \"Today\'s environment demands that we become more fuel- efficient and environmentally friendly, and as the launch Customer of the Boeing 737 MAX, we have accomplished both,\" Southwest CEO Gary Kelly said in a statement. \"Today\'s announcement will allow us to maintain our position as a low-cost provider in the years ahead,\"he said.Southwest, a low-cost airline based in Dallas, Texas, is the largest airline in the United States, based upon domestic passengers carried.