In 1955 Continental merged with Pioneer Air Lines, gaining access to 16 more cities in Texas and New Mexico. In August 1953 Continental flew to 35 airports and Pioneer flew to 19, but Continental's network didn't reach beyond Denver, El Paso, Houston and Kansas City until April 1957 when it started Chicago-Denver-Los Angeles, two Douglas DC-7Bs a day each way. Pioneer's Executive Vice President Harding Luther Lawrence arrived at Continental as a result of the merger. Bob Six commented on more than one occasion that, "the reason we bought Pioneer was to get Harding." Harding Lawrence implemented several innovative changes at Continental as well as a flamboyant advertising campaign during his ten years as Six's protege. During Lawrence's tenure Continental grew by 500 percent. Lawrence left Continental in April 1965 to head Braniff Airways.