What is a Flight Authorisation for? How do I get it?

A Flight Authorisation (also called Flight Permit) is a permit that is normally issued when the Airworthiness Certificate is temporarily invalid and the aircraft is required to fly for established reasons. 

The Authority or an Organisation with privileges may issue the Flight Authorisation provided it is under specified and approved flight conditions. There is a user manual for EASA aircraft and a user manual for NO EASA aircraft with instructions and information on how to obtain a Flight Authorisation. This manual also indicates how to carry out subsequent activities after obtaining the Certificate of Airworthiness, such as modifications, suspensions, etc.