Boeing announced Tuesday it will sell Southwest Airlines 208 airplanes, including 150 of its new 737 MAX aircraft, in the largest order ever for the US aerospace giant. \"Southwest is a special Boeing customer and has been a true partner in the evolution of the 737,\" Boeing Commercial Airplanes president and chief executive Jim Albaugh said in a statement heralding the deal, its largest ever both in terms of the number of planes and the dollar amount of the transaction.