Tourism started in Antarctica by the sea in the 1960s. Air overflights started in the 1970s with sightseeing flights by airliners from Australia and New Zealand, and were resumed in the 1990s. The (summer) tour season lasts from November to March. Most of the estimated 14,762 visitors to Antarctica from 1999–2000 were on sea cruises. During the 2009 to 2010 tourist season, over 37,000 people visited Antarctica. Tourism companies are required by the Antarctic Treaty to have a permit to visit Antarctica. Because no country owns Antarctica, countries which have signed the Antarctic Treaty issue permits, rather than visas. For example, an Australian traveling to Antarctica with a tourist company would need to show compliance with the Antarctic Treaty (Environment Protection) Act 1980 by means of an Environmental Impact Assessment (EIA) approved by the Australian Antarctic Division (AAD) of the Department of Agriculture, Water, and the Environment. Many sea cruises by cruise ships include a landing by RIB (Zodiac) or helicopter. Some land visits may include mountaineering, skiing or even a visit to the South Pole.