An aircraft becomes orphan when:
- the legal person holding the Type Certificate (TC) has ceased to exist. The TC automatically becomes invalid by law because there is no one to be in compliance with the TC holders responsibilities (21A.51 (a) 1 and 21A.44); or
- The TC holder no longer complies with his regulatory obligations. A typical case is when the TC holder loses his DOA, or fails to comply with 21.A.14 before 28.09.05. This makes the TC invalid (21A.51 (a) 1)
- The TC holder has surrendered the TC. This also makes the TC invalid (21A.51(a)2).
Under the current Part 21, orphan aircraft cannot be issued a Certificate of Airworthiness, which requires that a TC holder takes responsibility for the continued oversight of the design. They can therefore only continue to be operated if they hold a restricted certificate of airworthiness or a permit to fly. These documents can only be issued on the basis of a design approved by the Agency.