Definition
A gradual descent flown from cruising altitude toward the destination at or near cruise power, allowing the airplane to lose altitude while maintaining a relatively high airspeed and covering significant ground distance. It is typically planned and initiated well before the destination so the airplane arrives at pattern or approach altitude without abrupt power or configuration changes.
Plain English
A long, shallow descent started early so the airplane eases down from cruise altitude to traffic-pattern altitude over many miles, instead of staying high and dropping down quickly near the airport.
Context Anchor
You encounter this during flight planning and in flight when leaving cruise altitude for a lower altitude, an airport arrival, or a lower altitude assigned by air traffic control.
Derivation
"En route" comes from French, meaning "on the way." The phrase highlights that this descent is flown while still traveling toward the destination, not after arriving overhead.
Why Pilots Care
Allows efficient altitude management, fuel conservation, and compliance with arrival restrictions without speed or structural issues.
Intuition Check
Do not read “cruise” here as relaxed or casual. In aviation, cruise means the main traveling part of the flight after the climb and before the arrival or approach.
Example Sentence 1
About 80 miles from the destination, the pilot began a cruise descent at 500 feet per minute to arrive at pattern altitude without a steep drop near the airport.
Example Sentence 2
During the en route descent the airplane held 250 knots while losing altitude at 800 feet per minute.