Aviation Industry Glossary

A beginner's cheat sheet for understanding airline and aviation terminology used in this repository.

Quick Reference: Most Common Acronyms

Acronym	Meaning	One-Liner
PNR	Passenger Name Record	The 6-character booking reference (e.g., ABC123)
PSS	Passenger Service System	The airline's core booking/ticketing/DCS platform
OMS	Order Management System	Modern replacement for PSS - Orders as source of truth
DCS	Departure Control System	Check-in, boarding, and gate management
NDC	New Distribution Capability	IATA's modern API standard for airline shopping
GDS	Global Distribution System	Legacy booking networks (Amadeus, Sabre, Travelport)
EFB	Electronic Flight Bag	Pilot's iPad with flight documents
OCC	Operational Control Center	Nerve center for flight operations
IROPS	Irregular Operations	Disruptions (delays, cancellations, diversions)
RBD	Reservation Booking Designator	Legacy fare class letter (Y, B, M, etc.)

🎫 Booking & Orders

The Basics

Term	What It Means
PNR	Passenger Name Record - the classic 6-character booking code. Legacy identifier.
Order	Modern concept: everything a passenger bought in one transaction (seats, bags, meals).
Record Locator	Same as PNR - the booking confirmation code given to passengers.
Itinerary	The complete journey (all flights, connections, dates, times).
Segment	One flight leg (e.g., CCS→MIA is one segment).
Coupon	Each segment on a ticket has a coupon with a status (Open, Used, Void, etc.).

Order States (Our Model)

OFFERED → PAID → FULFILLED → COMPLETED
   │        │
   ↓        ↓
EXPIRED  CANCELLED

State	What It Means
OFFERED	Customer selected flights, hasn't paid yet (10-min hold)
PAID	Payment confirmed - now they can check in
FULFILLED	Passenger has flown
COMPLETED	All post-flight processing done
EXPIRED	Didn't pay within the hold window
CANCELLED	Refunded or voided

Passenger Types

Code	Type
ADT	Adult (12+)
CHD	Child (2-11)
INF	Infant (under 2, no seat)

💰 Inventory & Pricing

Legacy vs. Modern Inventory

Legacy (26 Classes)	Modern (P1-P5 Tiers)
F, A, J, C, D, I, Y, B, M, H, K, L, Q, T, V, X...	P1 (Premium) → P5 (Deep Discount)
Confusing, airline-specific meanings	Simple numerical tiers
Filed with ATPCO	Generated dynamically

Key Concepts

Term	What It Means
RBD	Reservation Booking Designator - the letter code (Y = full-fare economy).
Fare Basis	The detailed fare rule code (e.g., YOW30 = Y class, one-way, 30-day advance).
ATPCO	Airline Tariff Publishing Company - legacy fare filing system.
Cascading Availability	If P5 is available, P1-P4 are too (higher tiers include lower).
10-Minute Hold	Inventory is reserved for 10 minutes during checkout.
Overbooking	Selling more seats than available (accounting for no-shows).
Spoilage	Empty seats when a flight departs. Lost revenue.
Spill	Customers turned away because flight is full. Lost demand.

Pricing Formula (Dynamic)

Price = f(demand_signal, lead_time, inventory_position, customer_value)

Factor	Meaning
Demand Signal	How fast is this flight selling?
Lead Time	Days until departure (closer = higher price)
Inventory Position	How full is the plane?
Customer Value	Loyalty tier, booking history

✈️ Flight Operations

The Operations Control Center (OCC)

The OCC is mission control - they monitor all flights and handle disruptions.

Term	What It Means
Flight Release	Dispatch gives official approval for flight to depart.
IROPS	Irregular Operations - anything not going to plan.
Diversion	Landing somewhere other than planned (weather, medical, mechanical).
Ferry Flight	Empty positioning flight to move aircraft.
Deadhead	Crew flying as passengers to reposition.
AOG	Aircraft On Ground - plane can't fly (serious problem).
TAT	Turnaround Time - time between landing and next departure.

Crew Terms

Term	What It Means
FDP	Flight Duty Period - how long crew has been on duty.
Rest Requirements	Legal minimum rest between duties (FAA Part 117).
Reserve Crew	On-call crew ready to cover sick calls or delays.
Pairing	Multi-day sequence of flights assigned to crew.
Roster	Crew's monthly schedule.
Deadhead	Crew traveling as passenger to start a trip.

Aircraft Terms

Term	What It Means
MSN	Manufacturer Serial Number - unique aircraft ID.
Flight Hours (FH)	Total hours aircraft has flown.
Flight Cycles	Number of takeoffs/landings (affects maintenance).
MEL	Minimum Equipment List - what can be broken and still fly.
A/B/C/D Checks	Maintenance levels (A = light, D = heavy overhaul).

🛫 Departure Control (DCS)

Check-in Types

Type	Description
Agent Check-in	At the counter with a human
WOCI	Web Check-In (online)
Mobile Check-in	Via airline app
Kiosk	Self-service machine at airport

Boarding & Documents

Term	What It Means
BCBP	Bar Coded Boarding Pass (the 2D barcode on your pass).
PKPASS	Apple Wallet / Google Pay boarding pass format.
APIS	Advance Passenger Information - passport/visa data sent to destination.
Gate Reader	Scanner that reads boarding pass barcode.
Passenger Reconciliation	Final count before doors close.

Seat Assignment

Term	What It Means
Pre-reserved	Paid for specific seat in advance.
Auto-assigned	System picks seat at check-in.
Blocked Seat	Held for crew, operational reasons, or sold later.

⚖️ Weight & Balance (Load Control)

Every flight must be within weight limits and properly balanced.

Weight Terms

Term	What It Means
DOW	Dry Operating Weight - empty plane + crew + catering.
ZFW	Zero Fuel Weight - DOW + passengers + bags (no fuel).
TOW	Takeoff Weight - ZFW + fuel. Must be under max limit.
LDW	Landing Weight - TOW minus fuel burned.
%MAC	Center of Gravity as percentage of Mean Aerodynamic Chord.

Load Sheet

The load sheet is the final weight & balance document signed off before departure. Now digital (pushed to pilot's EFB).

OMS (Passenger Data) → Load Control → EFB (Pilot iPad)

💳 Payments & Settlement

Payment Terms

Term	What It Means
Form of Payment	How customer paid (card, cash, voucher).
Zero-Trust Vault	Payment system where servers never touch raw card data.
Tokenization	Replacing card number with secure token.
3D Secure	Extra verification step (password, SMS code).
Chargeback	Customer disputes charge - money clawed back.

Industry Settlement

Term	What It Means
BSP	Billing & Settlement Plan - how travel agents pay airlines (outside US).
ARC	Airlines Reporting Corporation - US equivalent of BSP.
Proration	Splitting revenue when multiple airlines carry one passenger.
ICH	IATA Clearing House - settles money between airlines.

Ticket Numbers

E-ticket format: PPP-FFFF-SSSSSS-C

Part	Meaning
PPP	Airline code (e.g., 052)
FFFF	Form serial
SSSSSS	Sequence number
C	Check digit

📡 Distribution & NDC

Traditional vs. Modern Distribution

Traditional (GDS)	Modern (NDC)
Text-based messages	JSON/XML APIs
Filed fares	Dynamic offers
Limited content	Rich content (images, bundles)
Amadeus, Sabre, Travelport	Direct API connections

NDC Key Concepts

Term	What It Means
Offer	What airline presents to customer (price, rules, products).
AirShopping	NDC endpoint to search flights.
OfferPrice	NDC endpoint to get final price.
OrderCreate	NDC endpoint to book the order.
ONE Order	IATA vision: single order replaces ticket + PNR + EMD.

Channel Types

Channel	Description
Direct	Airline website, app, call center
OTA	Online Travel Agency (Expedia, Booking.com)
TMC	Travel Management Company (corporate travel)
GDS	Global Distribution System (Amadeus, Sabre)
Aggregator	Google Flights, Skyscanner, Kayak

🏢 Industry Systems & Vendors

Core System Types

System	What It Does
PSS	Passenger Service System (reservations + inventory + DCS)
RM	Revenue Management (pricing optimization)
CRM	Customer Relationship Management
MRO	Maintenance, Repair & Overhaul
FFP	Frequent Flyer Program

Major Vendors

Vendor	Known For
Amadeus	Altéa PSS, GDS
Sabre	GDS, AirVision RM
SITA	Airline IT, messaging
Jeppesen	Flight planning, crew
IBS Software	iFlight suite
PROS	Revenue Management

📋 Standards & Regulations

IATA Standards

Standard	What It Covers
Resolution 792	Boarding pass barcode format
Resolution 797	ONE Order
NDC 21.3	Current NDC version
AHM	Airport Handling Manual
SSIM	Standard Schedules Information Manual

Regulations

Regulation	What It Covers
EU261	Passenger compensation rights (Europe)
FAA Part 117	US crew rest requirements
PCI-DSS	Credit card data security
GDPR	Data privacy (Europe)
IOSA	IATA safety audit

🛄 Baggage & Ground Handling

Baggage Messages (Type B)

Code	Message
BSM	Baggage Source Message (bag checked in)
BPM	Baggage Processed Message (bag sorted)
BTM	Baggage Transfer Message (connection)
BUM	Baggage Unload Message (bag loaded)

Ground Systems

Term	What It Means
CUTE	Common Use Terminal Equipment (shared check-in desks)
CUSS	Common Use Self Service (shared kiosks)
CUPPS	Common Use Passenger Processing (shared systems)

🎯 Special Situations

Disruption Types

Type	Example
Weather	Thunderstorm at destination
Mechanical	Aircraft has technical issue
Crew	Pilot sick, no reserve available
ATC	Air traffic control delays
Security	Security incident at airport

Passenger Services

Code	Service
WCHR	Wheelchair (to gate)
WCHC	Wheelchair (to seat)
VGML	Vegetarian meal
DBML	Diabetic meal
UM	Unaccompanied Minor
PETC	Pet in cabin

🔢 Quick Number Reference

Number	Meaning
6 characters	PNR/Record Locator length
13 digits	E-ticket number
26 letters	Traditional booking classes (A-Z)
5 tiers	Modern P1-P5 inventory model
10 minutes	Inventory hold window
15 minutes	Shopping offer validity
25-30 minutes	Target turnaround time
%MAC	Center of gravity measurement

📚 Further Reading

"The Order is the Single Source of Truth."