In the international visa system, the most common type of transit visa is the Type A (Airport Transit Visa). In the Schengen Area and many other jurisdictions, a Type A visa allows a traveler to stay within the "international zone" of an airport during a layover without officially entering the country. This is for passengers who are simply changing planes to a non-Schengen destination. If you need to leave the airport to stay in a hotel overnight or if you have to change airports (e.g., from Heathrow to Gatwick in the UK), you usually need a Type C (Short-stay) visa with a "transit" designation, as this involves passing through border control. Some countries also offer a Type B transit visa, though this has largely been phased out in favor of the Type C. In the United States, the specific transit visa is the C-1 Visa, which is required for any foreign national passing through the U.S. en route to another country, even if they never leave the airport. It is essential to check if your nationality requires an ATV (Airport Transit Visa), as many "visa-free" citizens still need an electronic authorization (like an ESTA or ETIAS) to transit.