EN ROUTE AIR TRAFFIC CONTROL SER‐VICES-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, capa-bilities, and controller workload permit, certain advisory/assistance services may be provided to VFR aircraft.
(See AIR ROUTE TRAFFIC CONTROL
CENTER.)
(Refer to AIM.)

EN ROUTE AUTOMATION SYSTEM (EAS)- The complex integrated environment consisting of situation display systems, surveillance systems and flight data processing, remote devices, decision support tools, and the related communications equipment that form the heart of the automated IFR air traffic control system. It interfaces with automated terminal systems and is used in the control of en route IFR aircraft.
(Refer to AIM.)
EN ROUTE CHARTS-
(See AERONAUTICAL CHART.)
EN ROUTE DESCENT- Descent from the en route cruising altitude which takes place along the route of flight.
EN ROUTE FLIGHT ADVISORY SERVICE- A service specifically designed to provide, upon pilot request, timely weather information pertinent to his/her type of flight, intended route of flight, and altitude. The FSSs providing this service are listed in the Airport/Facility Directory.
(See FLIGHT WATCH.)
(Refer to AIM.)
EN ROUTE HIGH ALTITUDE CHARTS-
(See AERONAUTICAL CHART.)
EN ROUTE LOW ALTITUDE CHARTS-
(See AERONAUTICAL CHART.)
EN ROUTE MINIMUM SAFE ALTITUDE WARN-ING- A function of the EAS that aids the controller by providing an alert when a tracked aircraft is below or predicted by the computer to go below a predetermined minimum IFR altitude (MIA).
EN ROUTE SPACING PROGRAM (ESP)-A program designed to assist the exit sector in achieving the required in‐trail spacing.
EN ROUTE TRANSITION-
a..
Conventional STARs/SIDs..The portion of a SID/STAR that connects to one or more en route airway/jet route.

b..
RNAV STARs/SIDs..The portion of a STAR preceding the common route or point, or for a SID the portion following, that is coded for a specific en route fix, airway or jet route.

ESP-
(See EN ROUTE SPACING PROGRAM.)
ESTABLISHED-To be stable or fixed on a route, route segment, altitude, heading, etc.
ESTIMATED ELAPSED TIME [ICAO]-The estimated time required to proceed from one significant point to another.
(See ICAO Term TOTAL ESTIMATED ELAPSED TIME.)

ESTIMATED OFF‐BLOCK TIME [ICAO]- The estimated time at which the aircraft will commence movement associated with departure.
ESTIMATED POSITION ERROR (EPE)-
(See Required Navigation Performance)
ESTIMATED TIME OF ARRIVAL- The time the flight is estimated to arrive at the gate (scheduled operators) or the actual runway on times for nonscheduled operators.
ESTIMATED TIME EN ROUTE- The estimated flying time from departure point to destination (lift‐off to touchdown).