Airline ticketing is a structured workflow involving airlines, global technology platforms, financial clearing organizations, and accredited intermediaries, all operating across a framework of international standards set primarily by the International Air Transport Association (IATA). Understanding how this process works matters to anyone who buys, sells, or builds technology around air travel because the rules governing each step directly determine price, availability, refundability, and accountability.
What An Airline Ticket Actually Is — And Why It Carries Legal Weight
An airline ticket is, at its most fundamental level, a document that confirms a passenger’s purchase of a seat on a specific flight. It can appear in paper or electronic form. Today, the overwhelming majority of tickets are digital, while physical paper tickets have become a rarity across most major markets.
The ticket carries three distinct legal and operational functions. First, it finalizes the commercial agreement between a passenger and an airline — it is, in effect, a contract of carriage. Second, it acts as a travel document confirming and securing seat and service allocation for a specific journey. Third, on itineraries involving more than one airline, the ticket governs the relationship between the carriers involved.
Step 1 — Flight Search: How Availability Reaches the Traveler Through 3 Different Channels
The airline ticketing process begins with a search. There are three main channels through which a traveler accesses flight availability, and each works differently.
Airline websites and direct booking platforms
When a passenger makes a website flight search, the query travels through the airline’s travel booking software to the carrier’s Central Reservation System (CRS). The CRS — which stores all flight schedules, seat inventory, fare rules, and booking classes — returns a list of available options for the selected dates and routes.
The CRS then returns a status code of HK (“holding confirmed”) when a seat is available, or UN when the carrier cannot fulfil the request. Most travelers choose to book directly with airlines because it is easier to change or cancel a reservation, and because airlines offer a broader range of ancillary services than are typically accessible through third parties.
Online Travel Agencies (OTAs)
For travelers building complex itineraries across multiple airlines, OTAs such as Expedia, Booking.com, or Kiwi.com aggregate flight data from multiple sources. They do this by pulling information from Global Distribution Systems (GDSs), which are large intermediary networks connecting airlines with travel sellers. Today, three GDS networks — Amadeus, Sabre, and Travelport — process the majority of indirect airline bookings worldwide.
According to Amadeus’s 2024 Annual Report, the company alone processed 1.7 billion total bookings in 2024, each generating a Passenger Name Record. GDS fees can account for up to 25% of ticket prices in the traditional distribution chain, a cost that has long motivated airlines to seek alternatives.
Metasearch engines
Platforms like Skyscanner, Google Flights, and Momondo collect data from OTAs and airline CRSs to display the widest possible range of flight options. They also pull data from low-cost carriers that typically do not distribute inventory to GDSs. Metasearch engines do not handle the booking themselves. They redirect the traveler to the airline’s own website or to an OTA to complete the purchase.
Step 2 — Booking: How A Passenger Name Record (PNR) Is Created
Once a traveler selects a flight, the retailer — whether an airline website or an OTA — verifies with the CRS that the option is still available at the same price. It then collects the traveler’s data to create a Passenger Name Record, or PNR.
A PNR is a unique booking file created at the time of reservation, holding everything needed to manage and service a trip from reservation to departure. Originally introduced by airlines in the 1960s to automate booking management, the format has become the universal standard across air, rail, hotel, and car rental systems worldwide. Each PNR is tied to a unique alphanumeric reference code, typically six characters, called a record locator — the code travelers receive by email immediately after booking.
Beyond the five mandatory IATA fields, a PNR can contain dozens of optional elements, including seat preferences, meal requests, loyalty program numbers, and special service requests (SSRs). The possible data points can expand to more than 60 items under IATA guidelines. An active PNR remains in the GDS until 24 to 72 hours after the last flight segment is flown, per the IATA Passenger Services Conference Resolutions Manual 2024.
It is critical to understand that a PNR and an e-ticket are not the same thing. A PNR confirms the reservation; an e-ticket confirms the right to travel. A booking can exist without a ticket — and this distinction becomes important in the payment step.
Step 3 — Ticketing And Payment: Why It Takes 3 Days for Money to Reach an Airline
Finalizing a booking requires payment — and this is where the complexity becomes most pronounced. Banks do not transfer money to airlines immediately. It can take three days or more to verify payment details and go through the entire confirmation process. This creates the gap between the moment a traveler receives a PNR number and the moment a ticket is actually issued.
The financial operations for a passenger booking directly on an airline’s website are handled through payment gateways — third-party services that process transactions and ensure data security. However, when full-service carriers, GDSs, and OTAs are involved, money must flow through two specialized financial clearing institutions: IATA’s Billing and Settlement Plan outside the United States, and the Airlines Reporting Corporation inside it.
Once payment is confirmed, the airline adds the fare data to the PNR. This record is then used to issue the e-ticket. The traveler finally receives a complete itinerary receipt to their designated email address, containing both the PNR reference and the 13-digit e-ticket number.
Ancillaries such as extra baggage, seat upgrades, or priority boarding are added to the PNR using IATA Special Service Request (SSR) codes. Each code contains four characters and corresponds to a specific service. Some airlines use proprietary codes that supplement the IATA system. Qatar Airways, for example, uses the code FALC to record the transport of falcons.
IATA ONE Order: The Single Record That Will Replace PNRs, E-Tickets, And EMDs
The most consequential change on the horizon for the airline ticketing industry is IATA’s ONE Order initiative. Today, one booking flow creates three separate documents: a PNR, an e-ticket, and an Electronic Miscellaneous Document (EMD) used to record ancillary fees. ONE Order is an XML-based standard designed to merge all three into a single, unified retail record available under a single reference number.
ONE Order extends NDC by transforming order management into a retail-like model — the same way most e-commerce stores operate. Managing a single record will help the airline create a single version of truth for each order in the sales pipeline. Storing and processing a single type of record also reduces the infrastructural resources required for billing and accounting.
The goal of this initiative is to simplify the booking process for travel agents, facilitate data sharing between airlines, and improve the experience of passengers who will no longer need to manage multiple reference numbers to track, change, or service a journey.
Most airlines are expected to transition fully to Offers and Orders architecture between 2028 and 2029, with widespread adoption unlikely before 2030 given the scale of legacy system replacement required. The transition demands that airlines dismantle long-standing organizational silos between their ticketing, reservations, and accounting departments.
