LOS ANGELES -- Abruptly reversing a course he set only two years ago, McDonnell Douglas Corp. chief executive Harry Stonecipher has said his company is abandoning its effort to be a leading builder of commercial jetliners. Stonecipher said Monday that McDonnell's Douglas Aircraft Co. division, which makes planes in Long Beach, California, will no longer develop the aircraft it would need to compete with industry leaders Boeing Co. and Europe's Airbus Industrie. Experts interpreted Stonecipher's message as a death knell for 75-year-old Douglas Aircraft, which today has a paltry 10 percent of the global jetliner market. Douglas builds the MD-90 and MD-80 single-aisle jetliners, the MD-11 wide-body and the new 100-seat MD-95. ""They're exiting the commercial business, there's no mistaking it,'' said Richard Aboulafia, an analyst with Teal Group, an aerospace research company in Fairfax, Virginia. McDonnell Douglas also is one of the United States' largest defense contractors.