OPLAN El Paso was a proposed campaign in the Vietnam War to block off the Laos trails by land. One southern and two American divisions would deploy by air and hold the terrain. This corps-sized blocking force could theoretically do what no amount of airpower realistically could: stop the flow of troops and supplies south.
It may have been a missed opportunity to decisively change the (conventional) course of the Vietnam war-or a chance for the northerners to inflict a huge number of politically sensitive casualties on the Americans in a place where it was near its supply bases and they were farther. If one of the people responsible for the plan was skeptical that it could work, you know it could very well end up going the way of the similar Lam Son 719.