persons employed or trained on aircraft, vessels, trains, trucks, buses, and any other means of international transportation, or ships fishing in international waters. Short-stay or visitor visas For short visits to the visited country. Many countries differentiate between different reasons for these visits, such as: Private visa, for private visits by invitation from residents of the visited country. Tourist visa, for a limited period of leisure travel, no business activities allowed. Medical visa, for undertaking diagnostics or a course of treatment in the visited country's hospitals or other medical facilities. Business visa, for engaging in commerce in the country. These visas generally preclude permanent employment, for which a work visa would be required. Working holiday visa, for individuals travelling between nations offering a working holiday program, allowing young people to undertake temporary work while travelling. Athletic or artistic visa, issued to athletes and performing artists (and their supporting staff) performing at competitions, concerts, shows, and other events. Cultural exchange visa, usually issued to athletes and performing artists participating in a cultural exchange program. Refugee visa, issued to persons fleeing the dangers of persecution, a war or a natural disaster. Pilgrimage visa: this type of visa is mainly issued to those intending to visit religious destinations and/or to take part in particular religious ceremonies. Such visas can usually be obtained relatively quickly and at a low cost; those using them are usually permitted to travel only as a group, however. The most well-known example is Saudi Arabia's Hajj visa. Digital nomad visa, for digital nomads who want to temporarily reside in a country while performing remote work. Thailand launched its SMART Visa, targeted at high expertise foreigners and entrepreneurs to stay a longer time in Thailand, with online applications for the visa being planned for late 2018. Estonia has also announced plans for a digital nomad visa, after the launch of its e-Residency program. Long-stay visas Visas valid for long term stays of a specific duration include: Student visa (F-1 in the United States), which allows its holder to study at an institution of higher learning in the issuing country. The F-2 visa allows the student's dependents to accompany them in the United States. Research visa, for students doing fieldwork in the host country. Temporary worker visa, for approved employment in the host country. These are generally more difficult to obtain but valid for longer periods of time than a business