Definition
A line on an airport drawing or layout plan beyond which buildings, fences, and other above-ground structures must not be built. It protects the airfield's runway and taxiway clearance areas, navigation aid signal zones, and required line-of-sight from the control tower.
Plain English
An invisible boundary on the airport that says: no buildings on this side. It keeps structures far enough away from runways and taxiways so that aircraft, signals, and tower visibility are not blocked.
Context Anchor
Seen on airport layout plans, airport development drawings, and some airport construction or planning documents.
Derivation
Built from three plain English words: 'building,' 'restriction' (from Latin restringere, to hold back), and 'line.' Together: a line that holds buildings back.
Why Pilots Care
Knowing the BRL location helps pilots anticipate where obstacles could affect low-altitude operations or instrument approaches.
Intuition Check
Do not read “building restriction line” as just a property boundary. In airport use, it is a safety and clearance limit for where buildings may be placed near aircraft operating areas.
Example Sentence 1
The proposed maintenance hangar had to be relocated because its original site fell inside the building restriction line.
Example Sentence 2
During preflight planning the student noted the BRL to understand why a proposed fuel farm could not be built closer to the runway.