Updated project metadata. This study explores the consequences of import failure in mammalian cells; wherein, blocking the import machinery has profound effects on mitochondrial ultra-structure and dynamics, but, surprisingly, does not impact import. The explanation is an astonishing response involving intercellular mitochondrial transfer via tunnelling nanotubes: for the import of healthy mitochondria and jettisoning of those with jammed import sites. These observations support the existence of a widespread mechanism for the rescue of mitochondrial protein import failure. Through proteomics, we identified proteins that interact with the trapped precursor, and may be involved in TNT signalling and formation.