Machu Picchu is a UNESCO World Heritage Site. As Peru’s most visited tourist attraction and major revenue generator, it is continually threatened by economic and commercial forces. In the late 1990s, the Peruvian government granted concessions to allow the construction of a cable car and development of a luxury hotel, including a tourist complex with boutiques and restaurants. These plans were met with protests from scientists, academics, and the Peruvian public all worried that the greater numbers of visitors would pose tremendous physical burdens on the ruins. A growing number of people visit Machu Picchu each year (400,000 in 2003). For this reason, there were protests against a plan to build a bridge to the site as well. A no-fly zone exists above the area. UNESCO is considering putting Machu Picchu on its List of World Heritage Sites in Danger. During the 1980s a large rock from Machu Picchu’s central plaza was moved out of its alignment to a different location in order to create a helicopter landing zone. Helicopter landings were forbidden in the 1990s. In 2006 a Cusco based company, Helicusco, sought to have tourist flights over Machu Picchu, but the decision was quickly overturned.