Definition
A reroute issued by Air Traffic Control before a flight departs, replacing the route the pilot originally filed in the flight plan. PDRRs are used by traffic management to balance traffic flow, avoid weather, work around airspace congestion, or comply with arrival restrictions at the destination. The new route is delivered to the pilot before pushback or taxi, typically through clearance delivery, and becomes the active route once accepted.
Plain English
A new route given to the pilot on the ground, before takeoff, that replaces the route they originally filed.
Context Anchor
You may encounter a PDRR during clearance delivery, before taxi or takeoff, when ATC gives you a route different from the one originally filed.
Derivation
Pre means before, departure means leaving the gate or runway, and reroute means a changed route. So a PDRR is literally a route change handed to the pilot before they leave.
Why Pilots Care
A PDRR can lengthen the route, increase fuel burn, or alter arrival time, so pilots must review the new clearance and update performance calculations before engine start.
Intuition Check
Do not assume a Pre Departure Reroute is just a suggestion or a planning note. In this context, it is an ATC-issued change to the route you are cleared to fly before takeoff.
Example Sentence 1
Before pushback, clearance delivery issued a PDRR sending the flight north of the original route to avoid a line of thunderstorms.
Example Sentence 2
Because of heavy departure volume, the traffic management unit issued a PDRR that added twenty minutes to the estimated time en route.