Formation flight. A flight consisting of more than one aircraf | ✈️Aviation English

Formation flight. A flight consisting of more than one aircraft which, by prior arrangement between the pilots, operates as a single aircraft with regard to navigation and position reporting, as well as clearances issued by ATC

Controllers do not provide separation between the formation elements but separate the formation itself (considered as a single flight) and other traffic depending on the applicable procedures (e.g. airspace class, RVSM procedures, etc.).