Citizens of certain countries must hold a short stay visa. The EU has a common list of countries whose citizens must have a visa when crossing the external borders and those whose nationals are exempt from that requirement. There are national derogations from the visa requirements for certain travellers.
Whether you are required to apply for a Schengen airport transit visa or not depends on your nationality.
Citizens of some countries must hold an airport transit visa when transiting through the international parts of airports situated in any of the Schengen States, while citizens of certain countries must hold an airport transit visa when transiting through the international parts of airports situated in some of the Schengen States.
You may be exempt from the airport transit visa requirement, if you: