Definition
Weather conditions and forecasts that apply along the planned route of flight between the departure and destination airports, used by pilots to anticipate hazards, plan altitudes, and make in-flight decisions during the cruise portion of a flight.
Plain English
The weather you expect to fly through on the way from where you took off to where you're landing — not the weather at takeoff or landing, but everything in between.
Context Anchor
Seen when reviewing weather sources before or during an instrument flight, especially when checking conditions along the planned path of flight.
Derivation
En route' comes from French, literally 'on the way' or 'on the road.' So 'en route weather' simply means 'weather on the way.'
Why Pilots Care
Affects altitude choice, fuel reserves, and decisions to deviate around hazards during the cruise portion of an IFR flight.
Intuition Check
Do not read en route weather as only the weather at the departure or destination airport. It means the weather along the path of the flight.
Example Sentence 1
Before departing, she reviewed the en route weather and noticed a line of thunderstorms forming across the second half of her route.
Example Sentence 2
While airborne, the crew requested updated en route weather to confirm clear conditions ahead.