Aren't mountain peaks, by definition, isolated? Then it should be understandable that using the wrong one in a tourism ad was an "isolated error," right? That, at least, was the explanation offered by embarrassed officials of Royal Nepal Airlines in apologizing for a recent promotional poster. "Have you seen Nepal?" the poster asked as the national carrier sought to help reinvigorate that vital sector of the economy following last year's chaotic street scenes between supporters and opponents of the monarchy, which have scared away visitors. Below those words appeared a four-color photo of a spectacular mountain scene. It might have gone all but unnoticed except for a sharp-eyed travelerwho spotted it on a wall in Royal Nepal Airlines' offices across the border in India's capital, New Delhi. As a proud Peruvian, Ernesto Malaga quickly recognized that the picture was not of Mount Everest or any other stately, snow-clad Himalayan summit, but of his own country's No. 1 tourism icon, Machu Picchu. Yes, the symbol of the ancient Inca empire. He alerted diplomats at Peru's embassy, who, in turn, contacted the carrier and asked for clarification. They got it, too, along with the news that "an employee in the rank of manager" had taken the fall for the boo-boo and been fired.