I was just thinking about aircraft that were not entirely successful or had been replaced in their original roles but bounced back to be successful when repurposed. This could include aircraft such as the Mustang or Avro Lancaster where the original designs were given a new lease of life with different engines and other modifications, but I was thinking more of aircraft like the Sterling, Typhoon, SM79 or Me110 which were for lack of a better phrase recycled and used successfully in a different role to that originally intended.