Acronyms

Acronyms & Terminology

Last updated: March 12, 2026

This reference defines acronyms and terminology used throughout PERTI and VATSIM traffic management.

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PERTI-Specific Terms

Acronym	Definition
PERTI	Plan, Execute, Review, Train, and Improve
DCC	Command Center
ADL	Aggregate Demand List - flight data feed containing schedules and NAS information
GDT	Ground Delay Tool
JATOC	Joint Air Traffic Operations Command
NOD	NAS Operations Dashboard
TMR	Traffic Management Review - NTMO Guide-style post-event review report (NEW v18)
TSD	Traffic Situation Display
NTML	National Traffic Management Log - record of TMI actions
SWIM	System Wide Information Management - PERTI's public API layer
FEA	Flow Evaluation Area - airspace element for traffic demand analysis
OpLevel	Operational Level 1-4 (traffic impact severity)
RBS	Ration By Schedule - GDP slot assignment algorithm
RBD	Ration By Distance - GDP variant distributing delay by flight distance
CASA	Compression After Slot Assignment - GDP compression algorithm
FPFS	First Planned First Served - GDP slot allocation by original ETA order
TVP	Table-Valued Parameter - SQL Server bulk data passing mechanism
ASPM82	FAA Aviation System Performance Metrics 82-airport set
OPSNET45	FAA Operations Network 45-airport performance metric set
CID	VATSIM Certificate ID (user identifier)
i18n	Internationalization - multi-language support system (NEW v18)

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Traffic Management

Acronym	Definition
TMI	Traffic Management Initiative
TMU	Traffic Management Unit
GS	Ground Stop
GDP	Ground Delay Program
AFP	Airspace Flow Program - controls departure times for flights arriving at an FCA
EDCT	Expect Departure Clearance Time
CTA	Controlled Time of Arrival - assigned arrival slot
ETD	Estimated Time of Departure
MIT	Miles-in-Trail
MINIT	Minutes-in-Trail
AAR	Airport Arrival Rate (arrivals per hour)
ADR	Airport Departure Rate (departures per hour)
SWAP	Severe Weather Avoidance Plan
CTOP	Collaborative Trajectory Options Program
FCA	Flow Constrained Area - airspace element used with AFPs
FEA	Flow Evaluation Area - airspace element for traffic analysis
CDM	Collaborative Decision Making
ATFM	Air Traffic Flow Management
DCT	Direct (routing between two points without following an airway)

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Airspace & Facilities

Acronym	Definition
ARTCC	Air Route Traffic Control Center (Center)
TRACON	Terminal Radar Approach Control
ATCT	Airport Traffic Control Tower
ATCSCC	Air Traffic Control System Command Center
SUA	Special Use Airspace
MOA	Military Operating Area
TFR	Temporary Flight Restriction
NSA	National Security Area
FIR	Flight Information Region
NAS	National Airspace System

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Flight Operations

Acronym	Definition
IFR	Instrument Flight Rules
VFR	Visual Flight Rules
SID	Standard Instrument Departure
STAR	Standard Terminal Arrival Route
DP	Departure Procedure
IAP	Instrument Approach Procedure
CDR	Coded Departure Route
PB	Playbook - pre-coordinated route play catalog
OOOI	Out-Off-On-In (flight phase tracking)
AFIX	Arrival Fix
DFIX	Departure Fix
ASECTR	Arrival Sector
DSECTR	Departure Sector

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Timing & Scheduling

TFMS uses a consistent prefix/suffix naming convention for times. Understanding this system helps interpret any timing acronym.

Prefix Meanings

Prefix	Meaning	Description
O	Original	Initial value before any modifications or delays
A	Actual	Recorded actual time (or Adjusted in some contexts)
P	Proposed/Predicted	Proposed time or prediction
S	Scheduled	Airline-scheduled time
C	Controlled	Time assigned by traffic management
E	Earliest/Estimated	Earliest possible or estimated time
L	Latest	Latest acceptable time
SR	Short Range	Estimate valid ~2 hours out
B	Baseline	Reference baseline time
I	Initial	Initial calculated time

Suffix Meanings

Suffix	Meaning	Description
TA	Time of Arrival	Arrival time (general)
TD	Time of Departure	Departure time (general)
ETA	Estimated Time of Arrival	Wheel-on time estimate
ETD	Estimated Time of Departure	Wheel-off time estimate
RTA	Runway Time of Arrival	Threshold crossing time
RTD	Runway Time of Departure	Runway departure time
GTA	Gate Time of Arrival	Gate arrival time (legacy, see note)
GTD	Gate Time of Departure	Gate departure time (legacy, see note)
TE	Time Enroute	Flight duration

Note on Gate vs Runway Times: TFMS renamed gate times to runway times:

• AGTA/AGTD → ARTA/ARTD (Actual Runway Times)
• OGTA/OGTD → ORTA/ORTD (Original Runway Times)

Some legacy systems may still reference the old gate time nomenclature.

Common Timing Acronyms

Estimated Times

Acronym	Definition
ETA	Estimated Time of Arrival (wheel time)
ETD	Estimated Time of Departure (wheel time)
OETA	Original Estimated Time of Arrival
OETD	Original Estimated Time of Departure
BETA	Baseline Estimated Time of Arrival
BETD	Baseline Estimated Time of Departure
ETE	Estimated Time Enroute
OETE	Original Estimated Time Enroute

Actual Times

Acronym	Definition
ATA	Actual Time of Arrival (wheels-on)
ATD	Actual Time of Departure (wheels-off)
ARTA	Actual Runway Time of Arrival (formerly AGTA)
ARTD	Actual Runway Time of Departure (formerly AGTD)

Controlled Times

Acronym	Definition
CTA	Controlled Time of Arrival
CTD	Controlled Time of Departure
OCTA	Original Controlled Time of Arrival
OCTD	Original Controlled Time of Departure
CETE	Controlled Estimated Time Enroute

Original/Baseline Times

Acronym	Definition
ORTA	Original Runway Time of Arrival (formerly OGTA)
ORTD	Original Runway Time of Departure (formerly OGTD)
OENTRY	Original Element Entry Time

Runway Times

Acronym	Definition
ERTA	Earliest Runway Time of Arrival
LRTA	Latest Runway Time of Arrival
SRTA	Short Range Time of Arrival (~2 hrs out)

Scheduled Times

Acronym	Definition
STA	Scheduled Time of Arrival
STD	Scheduled Time of Departure

Slot Times

Acronym	Definition
ASLOT	Arrival slot assigned to a flight (airport + time)
DSLOT	Departure slot assigned to a flight
Slot	Allocated arrival time in GDP/GS
R-Slot	Reserved arrival slot

Other Timing Terms

Acronym	Definition
P-Time	Proposed departure time
A-Time	Actual departure time
IGTA	Initial Gate Time of Arrival
AGT	Actual Ground Time (difference between ARTD and PGTD)

Time Difference Calculations

Acronym	Definition
OA_DIF	Difference between ARTA and ORTA
OD_DIF	Difference between ARTD and ORTD
PA_DIF	Difference between ARTA and PGTA

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Flight Status & Delay

Acronym	Definition
ALD	Airline-imposed delay (carrier delay status)
ARRD	Arrival Delay prediction
OUT	Actual gate pushback time (airline reported)
OFF	Actual wheels-up time (airline reported)
ON	Actual wheels-on time (airline reported)
IN	Actual gate arrival time (airline reported)

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Weather Categories

Acronym	Definition
VMC	Visual Meteorological Conditions
IMC	Instrument Meteorological Conditions
LVMC	Low Visibility Meteorological Conditions
LIMC	Low Instrument Meteorological Conditions
VLIMC	Very Low Instrument Meteorological Conditions

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Weather & Information

Acronym	Definition
ATIS	Automatic Terminal Information Service
METAR	Meteorological Aerodrome Report
TAF	Terminal Aerodrome Forecast
SIGMET	Significant Meteorological Information
AIRMET	Airmen's Meteorological Information
NEXRAD	Next-Generation Radar
MRMS	Multi-Radar Multi-Sensor
NOTAM	Notice to Air Missions
NCWF	National Convective Weather Forecast
NOWRAD	Current radar precipitation display

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Airport Categories

Acronym	Definition
Core30	30 busiest US airports by operations
OEP35	35 Operational Evolution Partnership airports
ASPM82	82 airports tracked in FAA Aviation System Performance Metrics
OPSNET45	45 airports in FAA Operations Network performance metric set
Pacing Airport	~30 larger airports whose traffic sets pace for CONUS operations

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Navigation

Acronym	Definition
VOR	VHF Omnidirectional Range
NDB	Non-Directional Beacon
DME	Distance Measuring Equipment
RNAV	Area Navigation
RNP	Required Navigation Performance
GPS	Global Positioning System
ILS	Instrument Landing System

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GIS & Spatial

Acronym	Definition
GIS	Geographic Information System - spatial data management and analysis
PostGIS	PostgreSQL extension for spatial/geographic data types and functions
WGS84	World Geodetic System 1984 - GPS coordinate reference system
SRID	Spatial Reference System Identifier (4326 = WGS84)
GeoJSON	JSON format for encoding geographic data structures
GIST	Generalized Search Tree - PostgreSQL index type for spatial queries
Adjacency Class	Type of boundary relationship: POINT (corner touch), LINE (shared border), POLY (overlap)
Boundary Adjacency	Graph network of which airspace boundaries share borders
Proximity Tier	Distance-based classification between boundaries (0-25nm, 25-50nm, 50-100nm, 100-200nm)
Shared Length	Length in nautical miles of common border between adjacent boundaries
Trajectory Crossing	Point where a flight path intersects an airspace boundary
Route Expansion	Process of converting route string to waypoint coordinates via GIS

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Systems & Data

Acronym	Definition
TFMS	Traffic Flow Management System (current system)
ETMS	Enhanced Traffic Management System (legacy, replaced by TFMS)
FSM	Flight Schedule Monitor
ASDI	Aircraft Situation Display to Industry
TFMDI	Traffic Flow Management Data to Industry
ASD	Aircraft Situation Display (legacy, replaced by TSD)
OAG	Official Airline Guide (schedule data source)
ARINC	Aeronautical Radio Inc.
CIFP	Coded Instrument Flight Procedures (DPs/STARs)
BADA	Base of Aircraft Data - EUROCONTROL aircraft performance model
ESE	Enhanced Sector Extensions - VATSIM sector definition file format
NASR	National Airspace System Resources - FAA navdata source
AIRAC	Aeronautical Information Regulation and Control - 28-day navdata cycle

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VATSIM-Specific

Acronym	Definition
VATSIM	Virtual Air Traffic Simulation Network
CID	VATSIM Certificate ID (user identifier)
VATUSA	VATSIM USA Division
VATCAN	VATSIM Canada Division
CANOC	Canadian Network Operations Centre (VATCAN traffic management)
ECFMP	EUROCONTROL-style Flow Management Position (used by VATSIM European divisions)
vATCSCC	Virtual Air Traffic Control System Command Center
CTP	Cross The Pond - major transatlantic VATSIM event
FNO	Friday Night Operations - regular VATSIM event
NTMO	National Traffic Management Officer

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Infrastructure & Technology

Acronym	Definition
PostGIS	PostgreSQL extension for spatial/geographic data
GIS	Geographic Information System
CDN	Content Delivery Network
HA	High Availability
DTU	Database Transaction Unit (Azure SQL performance metric)
vCore	Virtual CPU core (Azure SQL compute unit)
PERTI_MYSQL_ONLY	Optimization flag to skip Azure SQL connections (~500-1000ms saved)
PSR-12	PHP Standard Recommendation 12 (coding style)

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Communications

Acronym	Definition
ATC	Air Traffic Control
CTAF	Common Traffic Advisory Frequency
UNICOM	Universal Communications
FSS	Flight Service Station

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Aircraft & Organizations

Acronym	Definition
GA	General Aviation
ICAO	International Civil Aviation Organization
FAA	Federal Aviation Administration
CONUS	Continental United States

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GDP/GS Specific Terms

Term	Definition
Adaptive Compression (ADPT)	Moves flights up to fill wasted slots
AffAvgDelay	Affected Average Delay - total delay ÷ non-exempted flights
Blanket	GDP affecting all flights regardless of distance
DAS	Delay Assignment Strategy - GDP compression algorithm
Distance Tier	GDP scope based on flight distance from destination
ECR	EDCT Change Request - request to modify assigned departure time
GAAP	Ground Allocated Arrival Period - GDP slot methodology
Pop-up	Flight appearing in scope after program activation
Purge	Cancel a GDP/GS and release all assigned EDCTs
Recontrol	Re-assign EDCT to a previously controlled flight
Revision	Modification to an active GDP/GS
Slot Credit Substitution (SCS)	Swap flights between slots
UDP	Unified Delay Program - GDP variant with automatic compression

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Data Systems

Acronym	Definition
SWIM	System Wide Information Management - FAA data sharing program
STDDS	SWIM Terminal Data Distribution System
SFDPS	SWIM Flight Data Publication Service
AOC	Airline Operations Center
FIXM	Flight Information Exchange Model - XML standard for flight data
WXXM	Weather Information Exchange Model

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See Also

• FAQ - Frequently asked questions
• Glossary - Additional terminology