In what case doesn't a coupon correspond to a segment?

I read:

If you're flying AAA-BBB-CCC and then CCC-BBB-AAA, you might expect to have four coupons: AAA-BBB, BBB-CCC, CCC-BBB, and BBB-AAA. A coupon doesn't necessary correspond to a segment, however. – choster Jun 4 at 19:18

air-travel tickets

Best Answer

Just to add a source, an explanation on why indicating a land segment is used in airline reservation systems, and an example to choster's great answer, from the Wikipedia page on open-jaw tickets:

The open gaps between the cities show on the itinerary as ARNK, the same code that shows on an airline or agency's [Global Distribution System]. The term (pronounced arunk) means "arrival unknown".

The reason for this is that airline reservation systems (and major GDSs) require the segments following on sequentially, so arriving at one city, and then departing from another, will cause the system to return an error message. The ARNK field tells the system that this is intentional, and also allows for the ticketing system to blank the unused coupons of a ticket.

A typical destination open-jaw would look like this on an itinerary, with the ARNK on the second segment to show that it is not being flown on that ticket.

Segment 1: 11-NOV: SFO/IAD (San Francisco to Washington-Dulles)

Segment 2: ARNK: Arrival Unknown or Surface Transportation from IAD to PHL

Segment 3: 15-NOV: PHL/SFO (Philadelphia to San Francisco)

Also, here are the IATA definitions:

Term Name	Description	Source of Description
Coupon	The portion of the Passenger Ticket and Baggage Check or Excess Baggage Ticket that indicates particular places between which the coupon is good for carriage.
Segment	A leg or a group of legs from boarding point of a passenger to a deplaning point on a given flight.	IATA,PSCRMe34,CHPT 1,RESO 766
Segment	(Sometimes referred to as City Pair) The operation between board point and any subsequent off point within the same flight.	IATA,SSIMe38 (2011),CHPT 1.1,RP 1761b