Since 29 March 2007, EASA is responsible for the approval of the flight conditions on the basis of which a permit to fly can be issued by the Competent Authority of the Member State of Registry, or of the Member State prescribing the identification marks.A Permit to Fly is generally issued when a certificate of airworthiness is temporarily invalid, for example as the result of a damage, or when a certificate of airworthiness cannot be issued for instance when the aircraft does not comply with the essential requirements for airworthiness or when compliance with those requirements has not yet been shown, but the aircraft is nevertheless capable of performing a safe flight.More information here.
