Definition
A standard NOTAM contraction used to identify an obstruction or obstacle to air navigation, such as a tower, crane, building, or other structure that may pose a hazard to flight, particularly during takeoff, landing, or low-altitude operations.
Plain English
OBST is shorthand used in NOTAMs to flag something sticking up that pilots need to know about — a tower, crane, or other tall structure near an airport or along a flight path.
Context Anchor
Seen in NOTAMs, especially airport and runway notices, where temporary or fixed objects may affect aircraft operations.
Derivation
Short for 'obstruction' or 'obstacle.' NOTAMs use clipped contractions to keep messages short and quickly scannable, since they were originally transmitted by teletype where every character mattered.
Why Pilots Care
Failure to note an OBST can result in collision during takeoff, approach, or low-level flight.
Grounding Statement
Picture a crane set up near the end of a runway: even if the runway is open, that object may affect the safe path of an aircraft.
Intuition Check
Do not read OBST as just general clutter or something inconvenient. In a NOTAM, it means an obstruction that may matter to aircraft safety or clearance.
Example Sentence 1
The NOTAM read 'OBST TOWER 425 FT AGL 2NM SW OF AIRPORT,' so the pilot adjusted the departure to clear it safely.
Example Sentence 2
Before the night flight the pilot reviewed all OBST data on the approach plate.