A means employed by ATC to separate aircraft in terminal areas and en route airspace in the NAS. There are two methods employed to effect this separation:
- The tower controller sees the aircraft involved and issues instructions, as necessary, to ensure that the aircraft avoid each other.
- A pilot sees the other aircraft involved and upon instructions from the controller provides his/her own separation by maneuvering his/her aircraft as necessary to avoid it.
Source FAA Pilot/Controller Glossary · checked 2026-08-25