Definition
A descent conducted during the en route phase of flight, normally initiated and managed by ATC or in coordination with ATC, to transition the aircraft from its cruising altitude toward a lower altitude in preparation for arrival, an approach, or to comply with a clearance, traffic, or terrain requirement.
Plain English
Coming down from cruise altitude while still on the en route portion of the flight, before the arrival or approach segment really begins.
Context Anchor
Used in flight planning, ATC clearances, and arrival planning when deciding when to leave cruise altitude and begin descending toward the destination area.
Derivation
‘En route’ comes from French, meaning ‘on the way.’ So an en route descent is simply a descent made while still on the way — between departure and arrival phases — rather than during approach or landing.
Why Pilots Care
Enables compliance with ATC instructions for traffic separation and optimizes fuel burn by starting descent at the appropriate time.
Intuition Check
Do not read “en route descent” as any descent during a flight. It specifically means descending from cruise while still along the route, before the final landing segment.
Example Sentence 1
Center cleared us for an en route descent from FL350 down to 12,000 feet about a hundred miles before our destination.
Example Sentence 2
We began our en route descent early to avoid a line of thunderstorms ahead.