Definition
EN ROUTE AIR TRAFFIC CONTROL SERVICES
Air traffic control service provided aircraft on IFR flight plans, generally by centers, when these aircraft are operating between departure and destination terminal areas. When equipment, capabilities, and controller workload permit, certain advisory/assistance services may be provided to VFR aircraft.
- See: AIR ROUTE TRAFFIC CONTROL CENTER
Source: FAA Pilot/Controller Glossary (verbatim from the Federal Aviation Regulations).