Aviation Services Industry Terminology

A-CDM (Airport Collaborative Decision-Making)

A cross-stakeholder process (airport, ANSP, airlines, ground handlers) that shares accurate, timely data to optimize turnarounds, departures, and capacity. Improves predictability and reduces delays through milestones like TOBT/TSAT.

Airline updates TOBT, improving TSAT accuracy and reducing taxi delay - Sharing de-icing queue status helps sequence departures efficiently - Real-time turnaround milestones enable better gate and resource planning

ACARS (Aircraft Communications Addressing and Reporting System)

A digital datalink system for exchanging operational messages between aircraft and ground stations (OCC, maintenance, ATC via networks). Used for out/off/on/in times, weather, load sheets, and maintenance reports.

Crew transmits OUT/OFF/ON/IN times via ACARS - Dispatch uplinks revised route and winds to the cockpit - Aircraft sends maintenance fault codes to MX control over ACARS

ACMI (Aircraft, Crew, Maintenance, and Insurance)

A wet-lease model where the lessor supplies aircraft, crew, maintenance, and insurance; the lessee handles fuel, fees, and commercial risk. Common for peak season coverage and AOG recovery.

Airline wet-leases two A320s for summer peak coverage - ACMI arranged to cover schedule during an AOG event - Charter operator provides ACMI capacity to a startup carrier

AD (Airworthiness Directive)

A mandatory directive issued by an authority (e.g., FAA, EASA) requiring inspection, modification, or operational limitations to correct unsafe conditions. Must be complied with per specified timelines.

FAA issues AD requiring fan blade ultrasonic inspections - Operator complies with AD within 30 days per instructions - Maintenance revises records and tasks to include the new AD

ADS-B (Automatic Dependent Surveillance–Broadcast)

A surveillance technology where aircraft broadcast position, velocity, and status from onboard systems to ground stations and other aircraft. Improves situational awareness and ATC coverage.

Aircraft broadcasts position and velocity for ATC surveillance (ADS-B Out) - Flight tracking services display positions using ADS-B data - Cockpit receives traffic/weather on equipped aircraft (ADS-B In)

AOG (Aircraft on Ground)

A status indicating an aircraft is grounded due to a technical issue and requires urgent maintenance/parts to return to service. Drives premium logistics and rapid response.

A320 grounded for a failed hydraulic pump awaiting spares - AOG desk charters a go-now flight to deliver a component - Mobile repair team dispatched on the next flight to resolve AOG

APU (Auxiliary Power Unit)

A small turbine engine that provides electrical power and bleed air on the ground (and sometimes in flight). Used for air conditioning and engine start when GPU/ASU aren’t available.

APU supplies cabin air and power at a remote stand - Crew starts engines using APU bleed air - Ground power available, so APU is shut down to save fuel

Belly Cargo

Freight carried in the lower holds of passenger aircraft. Key revenue stream for network carriers and a planning variable for weight and balance.

Passenger 777 carries e-commerce parcels in the lower hold - Weight and balance accounts for ULDs loaded in the belly - Perishables are shipped as belly freight on long-haul flights

Block Time

The elapsed time from gate-out (blocks off) to gate-in (blocks on). Used in scheduling, crew duty, and performance metrics.

Schedule lists 1:45 block for the city pair - Crew duty limits are calculated using monthly block hours - Performance reports compare block time to airborne time

Codeshare

A commercial agreement where one airline markets and sells seats on another airline’s operated flight under its own flight number. Enables network expansion and seamless itineraries.

UA sells seats on an LH-operated flight under a UA flight number - Single PNR shows mixed-carrier itinerary via codeshare - Alliance partners extend network reach through codesharing

CRM (Crew Resource Management)

Training and operational philosophy emphasizing communication, leadership, decision-making, and teamwork to enhance safety and efficiency. Applies to flight deck, cabin, and ramp.

Flight deck briefing emphasizes communication and task sharing - Simulator debrief addresses CRM during an abnormal event - Cabin crew use CRM to coordinate a medical emergency response

DCS (Departure Control System)

Software used for passenger check-in, seat assignment, baggage tagging, weight-and-balance, and boarding. Integrates with inventory and load control.

Agent checks in passengers and assigns seats in DCS - DCS prints bag tags and transmits baggage data to BHS - Load control generates and sends the load sheet via DCS

De-icing/Anti-icing

Removal of ice/snow (de-icing) and application of fluids to prevent reaccumulation (anti-icing). Critical for airworthiness in winter ops; guided by holdover time tables.

Type I fluid used to remove ice, followed by Type IV for anti-ice - Crew calculates holdover time using HOT tables - Aircraft de-iced at a pad prior to taxi for departure

EASA Part-145

European regulation governing approval and oversight of maintenance organizations performing work on EU-registered aircraft. Requires MOE, personnel authorization, quality system.

MRO holds Part-145 approval to maintain A320 family - Certifying staff sign CRS per Part-145 authorizations - The MOE outlines procedures required by Part-145

EDTO/ETOPS (Extended Diversion Time Operations)

Regulatory framework permitting twin/aircraft operations on routes distant from suitable alternates, subject to maintenance, dispatch, and equipment requirements.

ETOPS 180 dispatch for North Atlantic routing - Dispatch confirms suitable en-route alternates and weather - Maintenance follows ETOPS program with pre-departure checks

EFB (Electronic Flight Bag)

Portable electronic system (often a tablet) hosting charts, performance, manuals, and apps replacing paper. Can integrate with ACARS and aircraft systems.

Pilots use EFB tablets for charts and manuals instead of paper - Performance app computes takeoff data and weights - EFB syncs updates via Wi‑Fi and integrates with ACARS

FAA Part 121

U.S. operational rules for domestic, flag, and supplemental air carriers. Covers training, maintenance programs, MEL usage, dispatch, and safety systems.

Airline operates revenue flights under a Part 121 certificate - MEL usage and dispatch requirements follow Part 121 - Training curriculum and checking approved under Part 121

FBO (Fixed-Base Operator)

A company providing GA/Business aviation services: fueling, hangar, ground handling, crew amenities. Often the primary service interface for corporate jets.

Bizjet refuels and parks at the FBO with crew amenities - Ground handling for a corporate flight arranged via the FBO - FBO coordinates customs and catering for an arrival

FOD (Foreign Object Debris/Damage)

Debris on the ramp/runway that can damage aircraft; also the resulting damage. Managed via inspections, housekeeping, and tool control.

Ramp sweep finds a screw near Gate B12 preventing FOD - Tool control prevents items being left in the engine bay - Engine suffers FOD damage after ingesting debris on taxiway

FOQA (Flight Operations Quality Assurance)

A proactive safety program analyzing recorded flight data to identify trends, exceedances, and training needs. Often part of SMS.

Analysis flags unstable approach rates at specific airport - FOQA trends trigger targeted training for crews - SMS action item created to address FOQA exceedances

GPU (Ground Power Unit)

Ground equipment that supplies electrical power to aircraft during turnarounds, reducing APU use, fuel burn, and emissions.

Ramp connects GPU to power avionics during turnaround - GPU use reduces APU fuel burn and emissions - Technician verifies correct voltage/frequency before power-on

GSE (Ground Support Equipment)

Equipment used to service aircraft on the ground: tugs, belt loaders, stairs, lav trucks, catering trucks, ASUs, GPUs, de-icers.

Belt loader positions at rear cargo door for unloading - Lavatory service truck services the aircraft - Tug and towbar used for pushback from the gate

Hub-and-Spoke

Network model concentrating flights at hub airports to facilitate connections and maximize aircraft/crew utilization. Affects scheduling, MCTs, and resource planning.

Hub banks timed for optimal connections at 0900/1100 - Itinerary uses a hub to connect two spokes within MCT - Spoke flights feed long-haul departures from the hub

IATA (International Air Transport Association)

Trade association setting commercial standards (ticketing, baggage, SGHA), managing settlement systems, and auditing (IOSA). Maintains IATA airport/airline codes.

Airline maintains IOSA registration through IATA - Station contracts ground handling using the IATA SGHA - IATA codes used: LHR (airport) and BA (airline)

ICAO (International Civil Aviation Organization)

UN specialized agency issuing global Standards and Recommended Practices (SARPs) and guidance (Annexes). Basis for national regulations and procedures.

Compliance with ICAO Annex 14 for aerodrome standards - State files differences to ICAO SARPs in its AIP - ICAO 4-letter codes used for airports (e.g., KJFK, EGLL)

Interline

Agreements enabling carriers to accept each other’s tickets and baggage, often with settlement/proration. Facilitates through-checking and disruption recovery.

Through-check baggage on AA to BA via interline agreement - Revenue settled via interline proration and clearing house - IROP reaccommodation uses interline partners to reroute PAX

IROP (Irregular Operations)

Disruptions to planned schedule due to weather, ATC, maintenance, crew, or airport constraints. Requires playbooks for reaccommodation and recovery.

Snowstorm forces widespread cancellations and diversions - ATC flow program causes rolling departure delays - Aircraft swap due to maintenance creates misconnects

IOSA (IATA Operational Safety Audit)

A standardised audit program assessing an airline’s operational management and control systems. Often required for alliance membership and codeshares.

Airline completes IOSA to join a global alliance - Biennial IOSA renewal audit verifies continued conformity - Corrective action plan addresses IOSA findings

Jet A-1

International kerosene-based turbine fuel with specific freezing point and flashpoint specs; in the U.S., Jet-A is common. Stored, handled, and tested under strict standards.

Fueler uplifts Jet A-1 for an intercontinental flight - Density and temperature checks recorded during fueling - Cold-weather ops consider Jet A-1 freezing point margins

KPI (Key Performance Indicator)

Quantitative metric to track performance against targets. Common aviation KPIs: OTP, mishandled bags/1,000 PAX, fuel burn per block hour, turnaround punctuality.

OTP D+15 tracked at 85% against a 90% target - Mishandled bags per 1,000 PAX monitored monthly - Fuel burn per block hour benchmarked by fleet type

Line Maintenance

Maintenance performed during transit/overnight stops, including inspections, troubleshooting, defect rectification, and minor checks. Rapid response to support dispatch.

Transit check performed at an outstation between legs - MEL item rectified overnight during a layover - Troubleshooting a snag at the gate to support dispatch

Load Factor

Percentage of available seat capacity actually filled by paying passengers (RPK/ASK). Core commercial efficiency metric.

Monthly load factor reached 92% on the route - Yield decreased while load factor increased year-over-year - RM adjusts fares to target a higher load factor

MCT (Minimum Connection Time)

The shortest permissible time for a legal connection at an airport, varying by terminal, airline, and international/domestic status.

JFK Terminal 4 INTL-DOM MCT is 75 minutes - Schedule builders verify legal connections meet MCT - Rebooking tool checks MCT during disruption handling

MEL (Minimum Equipment List)

An operator-specific document, derived from the MMEL, listing equipment that may be inoperative for dispatch and the conditions/procedures to follow.

Dispatch permitted with inoperative APU under MEL conditions - Operations placard applied and procedures followed per MEL - MEL deferral categorized as B with a 3-day limit

MRO (Maintenance, Repair, and Overhaul)

The sector and activities covering scheduled checks, heavy maintenance, component repair, and modifications for aircraft and engines.

Aircraft undergoes a C-check at a third-party MRO - Engine sent to shop for performance restoration overhaul - Component repaired via rotable pool exchange at MRO

NOTAM (Notice to Air Missions)

Time-critical aeronautical information on facilities, procedures, or hazards not published elsewhere. Essential for flight planning and ramp operations.

NOTAM advises RWY 09/27 closed for resurfacing - Flight planning includes a review of active NOTAMs - Crane near approach path published via NOTAM

PAX (Passengers)

Industry shorthand for passengers. Widely used in operations, planning, and reporting.

Load sheet shows 150 PAX boarded with 5 infants - Connecting PAX protected due to inbound delay - Vouchers issued to PAX during a long delay

Pushback

The operation of moving an aircraft away from the gate using a tug, typically to align for taxi. Requires coordinated clearances and headset comms.

Ground crew obtains clearance and begins pushback - Towbar attached to nose gear; headset comms established - Engines started during pushback to Spot 32

RASM (Revenue per Available Seat Mile)

Total operating revenue divided by available seat miles (or RASK per kilometer). Measures revenue productivity relative to capacity.

Quarterly RASM up 3% driven by higher fares - Market-level RASM compared across routes for optimization - Positive RASM-CASM spread indicates healthy margins

SAF (Sustainable Aviation Fuel)

Drop-in jet fuel from sustainable feedstocks that reduces lifecycle CO2 compared to fossil Jet A/Jet A‑1. Subject to ASTM certification and blending limits.

Airline operates flight using a 30% SAF blend - Carrier signs multi-year SAF offtake agreement - Corporate customer uses book-and-claim SAF certificates

SB (Service Bulletin)

Manufacturer-issued recommendation for modifications, inspections, or procedures. May be optional or later mandated by an AD.

OEM issues SB to reinforce pylon bracket assemblies - Operator incorporates SB during the next maintenance visit - SB later referenced by a mandatory AD

SGHA (Standard Ground Handling Agreement)

IATA contract template defining ground handling services, responsibilities, and liability with Annex A (services) and Annex B (charges).

Airline signs SGHA with a handler at FRA - Annex A lists services such as pushback and baggage - Annex B defines per-turn charges and rate adjustments

SIDA (Security Identification Display Area)

Controlled airport area where personnel must display proper identification and comply with security procedures. Access requires vetting and training.

Ramp staff must display SIDA badges at all times - New hires complete SIDA training and background checks - Visitors require escort within the SIDA

Slot (ATC/Airport Slot)

Allocated permission to schedule an arrival/departure at a coordinated airport or a controlled takeoff time via ATC flow. Drives network planning and OTP.

Airline requests summer season slots at a Level 3 airport - ATC issues a CTOT slot due to en-route restrictions - Slot usage tracked against the 80/20 rule

SMS (Safety Management System)

A systematic approach to managing safety risk, including policy, risk management, assurance, and promotion. Required by many regulators.

Employee submits a hazard report via the SMS portal - Risk assessment conducted with mitigations assigned - Safety assurance audit verifies controls are effective

TAT (Turnaround Time)

Elapsed time from block-in to block-out. Core driver of utilization, OTP, and gate/resource planning.

Target TAT reduced from 45 to 40 minutes to boost utilization - Turnaround Gantt chart tracks key milestones - Catering delay extends TAT and affects OTP

ULD (Unit Load Device)

Standardized aircraft cargo containers and pallets (e.g., LD3, PMC) used to load baggage and freight efficiently and safely.

LD3 containers loaded in the widebody belly hold - PMC pallet secured with nets before loading - ULD control system tracks container inventory and damage

Wet Lease

A lease where the lessor provides aircraft and crew (often ACMI), while the lessee covers fuel, fees, and commercial risk. Used for capacity flexibility and disruptions.

Airline wet-leases an A330 with crew for six months - Short-term wet lease covers schedule during heavy checks - ACMI contract sets hourly rates and performance terms

Yield

Average revenue per passenger mile/kilometer; indicates pricing strength. Often evaluated with load factor to assess profitability.

Average passenger yield increases after fare adjustment - Premium-cabin yield outperforms economy on business routes - RM balances yield and load factor to maximize revenue

Zulu Time (UTC)

Coordinated Universal Time used as the standard in aviation operations for schedules, NOTAMs, flight plans, and weather.

Flight plans and logs recorded in Zulu (UTC) time - NOTAM validity shown as 1200Z to 1800Z - Operations control room runs on a UTC clock