NOTAM abbreviations and contractions

Why are NOTAMs written in abbreviations at all?

NOTAM shorthand is a leftover from teleprinter distribution, when every character cost transmission time and messages had to survive noisy links. The format stayed because it is compact, unambiguous once you know it, and language-neutral across borders — CLSD means the same thing to a pilot in Lagos as it does to one in Chicago.

The cost is that a NOTAM package reads as a wall of capital letters. The contractions themselves are not difficult; there are simply a lot of them, and they arrive without spacing or punctuation to help you. Learning the thirty or so that appear in almost every surface notice removes most of the difficulty.

The NOTAM abbreviations you will meet most often

This table covers the contractions that appear repeatedly in airport and surface NOTAMs. It is a working list for reading notices, not a complete official glossary — the full authority is the FAA contractions order linked at the foot of this page.

Contraction	Meaning
AD	Aerodrome
ACFT	Aircraft
AGL	Above ground level
AMSL	Above mean sea level
APCH	Approach
APN	Apron
ARR	Arrival
AVBL	Available
BTN	Between
CLSD	Closed
CNL	Cancelled
CTC	Contact
DEP	Departure
DLY	Daily
DISPLACED THR	Displaced threshold
EXC	Except
FICON	Field condition
FREQ	Frequency
HIRL	High intensity runway lights
ILS	Instrument landing system
LGT / LGTD	Light / lighted
LDA	Landing distance available
MAINT	Maintenance
MIRL	Medium intensity runway lights
NAVAID	Navigational aid
OBST	Obstacle
PAPI	Precision approach path indicator
PERM	Permanent
PSN	Position
REIL	Runway end identifier lights
RWY	Runway
SFC	Surface
SR	Sunrise
SS	Sunset
TFC	Traffic
THR	Threshold
TEMPO	Temporary
TWY	Taxiway
U/S	Unserviceable
UFN	Until further notice
WEF	With effect from
WIP	Work in progress

Contractions that change what a closure means

A handful of contractions do more than name a thing — they change the scope of the closure, and misreading them is where errors happen:

• BTN (between) — limits the closure to one segment. TWY B CLSD and TWY B BTN TWY A AND TWY K CLSD are very different notices.
• EXC (except) — carves an exception out of a closure, for example a taxiway closed except for a named aircraft category.
• DLY (daily) — the closure repeats in a daily window rather than running continuously across the whole date range.
• SR / SS (sunrise / sunset) — the times move with the calendar rather than being fixed clock hours.
• U/S (unserviceable) — the facility exists but cannot be relied on; this is not the same as closed.
• WEF (with effect from) and UFN (until further notice) — an open-ended notice with no published end.

Read the whole line before deciding what it means. A closure with DLY in it can be irrelevant to your slot or completely blocking, depending only on the hours.

Frequently asked questions about NOTAM abbreviations

What does CLSD mean in a NOTAM?

CLSD is the NOTAM contraction for closed. It is used for runways, taxiways, aprons and other surfaces, for example TWY B CLSD, and is normally followed by an effective date-time period in UTC.

What does WIP mean in a NOTAM?

WIP stands for work in progress. It indicates construction or maintenance activity, and often appears alongside CLSD to give the reason a taxiway or runway is closed.

What is the difference between U/S and CLSD?

U/S means unserviceable and CLSD means closed. An unserviceable facility such as a light or navigation aid still exists but cannot be relied upon, whereas a closed surface may not be used at all.

Where is the official list of NOTAM contractions?

The authoritative list for United States NOTAMs is the FAA contractions order, published as FAA JO 7340.2, with NOTAM-specific guidance in FAA JO 7930.2. ICAO Doc 8400 covers the international abbreviations used in ICAO-format NOTAMs.

Do NOTAM abbreviations mean the same thing in every country?

Most core contractions such as RWY, TWY and CLSD are used consistently under the ICAO format, but national systems vary in detail and some domestic contractions are local. Always read notices against the abbreviation list published by the relevant authority.

Always verify with official sources

TaxiwayClosed AI is an awareness and training aid — it is not an official briefing and is never a substitute for one. Before any real flight, pull the current package from official sources such as FAA NOTAM Search, review the procedures in the FAA JO 7930.2 NOTAM order and in SKYbrary, use your approved EFB briefing, and confirm anything unclear with ATC, dispatch, or your CFI.