How E-Ticket Numbers Are Structured

An e-ticket number is thirteen digits, and none of them are arbitrary. Knowing how it is put together explains several things that otherwise look like system errors — why a number is rejected instantly, why a partially flown ticket has extra digits on the end, and why the airline whose code starts your ticket may not be the one flying you.

For what an e-ticket number is and where to find yours, see e-ticket number explained. This page is about the anatomy.

The three parts

125 - 2412345678
 │         │   │
 │         │   └── check digit
 │         └────── serial number
 └──────────────── airline accounting code

The first three digits are the airline’s numeric accounting code, assigned by IATA. It identifies whose ticket stock the document was issued on.

The next nine are the serial, allocated sequentially from the ranges the airline holds.

The last is a check digit, computed from the twelve before it.

The airline prefix

This is the part with real information in it. A few you will meet often:

Code	Airline
001	American Airlines
006	Delta Air Lines
016	United Airlines
057	Air France
074	KLM
105	Air Canada
125	British Airways
157	Qatar Airways
176	Emirates
235	Turkish Airlines
618	Singapore Airlines

Note that this numeric code is a third identifier, separate from the two-letter IATA designator in your flight number and the three-letter ICAO code used by air traffic control. BA, BAW and 125 all mean British Airways in three different contexts. The airline code lookup covers the first two; the numeric one appears only here.

Why the prefix may not match the airline you fly

On an interline journey, one carrier issues the ticket and others honour it. Your ticket can begin 125 while the aircraft you board belongs to someone else entirely.

That is not an error, and it matters when something goes wrong: the issuing airline generally controls the ticket, so a change or refund usually goes through them rather than the carrier that flew you. Combined with the marketing-versus-operating distinction in airline codes explained, a single journey can involve three different airlines in three different roles.

Coupon suffixes

A ticket has one coupon per flight segment. On a multi-segment ticket you may see the number written with an extra digit or two:

125-2412345678-1     first coupon
125-2412345678-2     second coupon

Each coupon is consumed as you fly it. This is the mechanism behind a rule that catches people out: coupons must generally be used in sequence. Skip the first segment and the rest of the ticket is typically voided automatically — which is why missing an outbound flight can cancel your return.

It is also why an agent can tell you exactly which parts of a ticket remain unused.

The check digit

The final digit is a modulus-7 check: take the first twelve digits as an integer, divide by seven, and the remainder is the check digit.

It exists because these numbers were once read aloud and typed by hand, and a transposed pair of digits would otherwise retrieve someone else’s ticket. With the check digit, a mistyped number is almost always rejected outright rather than silently resolving to the wrong record.

Practically, this is why an invented ticket number fails immediately rather than merely returning “not found” — it usually fails validation before any lookup happens at all.

When the number does not work

Wrong number. Agency booking numbers and PNR codes get mistaken for ticket numbers. A ticket number is thirteen digits; a PNR is six alphanumeric characters. See what is a PNR number.

No ticket was issued. You may hold a reservation that was never ticketed. There is no number to find. See flight reservation vs ticket.

The ticket was reissued. A change generates a new ticket number and voids the old one. Quote the current one.

You are asking the wrong airline. Check the prefix against the table above; the issuing carrier may not be the operating one.

Why a sample itinerary has none

The structure above is the reason the generator on this site prints SAMPLE — NOT ISSUED rather than a number.

Producing a plausible e-ticket number means borrowing a real airline’s accounting prefix and computing a valid check digit — that is, manufacturing something built to survive a first-pass validation against a specific carrier’s identity. There is no version of that which is a planning aid. Leaving it blank costs nothing to anyone laying out a trip.

E-ticket number explained — the guide this supports
What is a PNR number? — the other code on your itinerary
Airline codes explained — IATA, ICAO and flight numbers