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			Originally Posted by Bhavshah
			
		
		
I had always read in the past one should read about Interlining and how it works. It took me a while to search and put my understanding together from whats on the net. I am now putting publicly posted and widely available information together so that it may be useful to the noob..the Senseis can skip this intro.. BTW, although i have taken great care; If anyone feels I have disclosed anything sensitive then do, please PM me; and I will edit...

All (apart from highly complicated tricks on specific OTAs which we will not get into) tickets which you are looking to dump must have EoE allowed. Unless the airline is self-dumping, most dumps arise due to multi-carrier Itins. 

Multi-carrier itins are possible due to Interlining (also known as "interline ticketing") which is a voluntary commercial agreement between individual airlines to handle passengers traveling on itineraries that require multiple airlines. When you book a multi carrier itin, the system will automatically select a plating (also called a validating carrier/ issuing carrier) which is the airline that validates or issues tickets, and the one that receives the money when the flights are booked. In the event of cancellations this is the carrier with which the flyer has credit. 

The itinerary would actually show the different airlines eg Leg 1 flown by UA followed by Leg 2 flown by AA etc. Interline agreements are directional. For example, it may be possible for American Airlines to issue the ticket on an American-United itinerary but United might not be able to be issuer on the same itinerary.

Interlining agreements differ from codesharing agreements in that codesharing agreements usually refers to numbering a flight with the airline's code (abbreviation) even though the flight is operated by another airline. However, codeshare relationships can affect whether an interline ticket (or e-ticket) can be issued. Both the codeshare marketing carrier and codeshare operating carrier (which owns and is flying the metal) must have interline agreements with all other carriers in the itinerary to allow a single ticket to be issued. 

Most full service airlines have an interlining agreement with their alliance members and also with competitors in other alliances or independents. The full Master list of Interlining is available on line to purchase at $461 - maybe thats where WWE based his Universal YQ remover from :p

 Most newer low-cost carrier airlines that only sell directly to consumers (and not through agencies or GDS systems) do not support interlining at all. For example, United Airlines does not have an interline agreement with Southwest Airlines or Easyjet. So searching for a UA dump on Easyjet will not be fruitful

Most online travel agencies will only display itineraries that can be ticketed on one of their booking systems. However Orbitz will sometimes display un-ticketable interline itineraries. Examples could be found previously on routes to Mexico involving the now defunct Aero California or on routes to Indonesia involving Lion Air. These are displayed on Orbitz as "contact airline to buy"

Hacker fares shown by Kayak are often examples of NON interlining single tickets sold to the unsuspecting public. Two separate tickets will need to be issued and passengers will have to retrieve their bags and carry it to the connecting airline for check-in. Itineraries with interline connections such as this are risky for travelers since the second carrier may be unaware of delays or issues with the incoming flight and it is more likely for luggage to be lost.

Anyway assuming an interlining agreement is present between two or more carriers, a single eticket itin can be put together. Before we proceed further we have to understand how IATA subdivides its zones (which is different from C1, C2 etc on our threads)

The world is divided into three big Travel Conference Areas- 
TC1 has North and South America.
TC2 has Europe, the Middle East, and Africa.
TC3 has Asia and Oceania.

Each TC area has a Sub-areas:
TC1: North America; Central America; Caribbean; South America
TC2: Europe; Middle East; Africa
TC3: Japan and Korea; South Asian Subcontinent; South East Asia; South West Pacific 

Divisions generally respect country (ie the entire country is invariably in one Area) except Russia which is in both TC2 and TC3, divided by the Urals.

When there is a single Carrier PNR, the system will calculate the YQ/YR Surcharge based on that airline. If there is more than one airline, Amadeus follows the Default Validating Carrier Processing for YQ/YR for the calculation of YQ/YR taxes, in case of interlining/end-on-end itineraries. 

Following are the check points done by system in back-end to return most appropriate Validating Carrier,
A) BSP participation (entry is TGBD-XX, where XX is the country code)- The BSP is a system designed to facilitate and simplify the selling, reporting and remitting procedures of IATA Accredited Passenger Sales Agents

B) GSA table (entry is TGGSD-XX, where XX is the country code)...A general sales agent (GSA) is a sales representative for an airline in a specific country or region. Typically, the GSA is responsible for selling all products of the airline in its region which includes flight tickets and cargo space. A GSA will typically sell the product of more than one airline.

C) Interline agreement table (entry is TGAD-XX/YY, where XX is validating carrier and YY is the operating/marketing carrier)

D) ATPCO default validating carrier logic, which has following sub-conditions:

1. When the entire journey is same as country: carrier on the first segment is Validating Carrier. 

Example: MUC - FRA (Carrier LH) FRA - BER (Carrier LT) BER - HAM (Carrier DE) All the sectors are in Germany, so the default validating Carrier is LH. .

Implication- If you are looking to dump a multi carrier itin within the same country, its more likely to be a 1x then a 3x. You should look for a carrier with Low YQ/YR for the first leg.


If the first condition is not matched, the system analyses condition number 2

2.When the journey is within the same IATA Sub-area: carrier on the first 
international sector of the journey is Validating Carrier. 
Example: DEL-BOM (Carrier 9W) BOM - CMB (Carrier UL) CMB - BKK (Carrier TG ) All the sectors are in the same IATA sub-area "South Asian Sub-continent", and the first international sector is between India and Sri Lanka, so the default validating Carrier is UL. I could be wrong but if UL does not have a GSA or official airline presence in the country then it would go to TG (needs to be confirmed by Senseis) although with the OTA world I think this restriction is outdated

Implication- If you are looking to dump a multi carrier itin within the same Sub Area, then your X will be where your itin first crosses between two countries - you should look for a carrier with Low YQ/YR for that leg.


If the second condition is not matched, the system analyses condition number 3.

3. When the journey is within the same TC area: Carrier on the first segment which crosses IATA sub-area is the Validating Carrier.
Example: MAD - PAR (Carrier IB) PAR - FRA (Carrier AF) FRA - CAI (Carrier LH) A IATA sub-area has been crossed between FRA and CAI and all the sectors are in the same TC area (TC2), so the default validating Carrier is LH.

Implication-Say you wanted to fly MAD-PAR-FRA, (the first two flights in the example) but there was a large YQ. If you add another flight that crosses a sub-area (like FRA-CAI) at the end of your itinerary, that carrier will be defaulted as the validating carrier. If it has low YQ you may be able to massage the system

If the third condition is not matched, the system analyses condition number 4. 

4. When the itinerary encompasses exactly two TC areas, then the carrier on the segment which crosses TC area is the Validating Carrier.
Example: MAD - PAR (Carrier IB) PAR - SIN (Carrier SQ) There has been a crossing between TC2 and TC3 area (sector PAR-SIN), so the default 
validating Carrier is SQ.

I think by now you should be able to draw your own implications:D

If the fourth condition is not matched, the system analyses condition number 5. 

5. When the itinerary encompasses exactly three TC areas, such as 'Round The World'  then:

a.If the two crossings of TC areas are between TC3 and TC2 and 
between TC2 and TC1, then the selected Validating Carrier is the 
Carrier from the first sector that crosses between TC2 and TC1. 

b. If the two crossings of TC areas are not between TC3 and TC2 and 
between TC2 and TC1, then the selected Validating Carrier is the 
Carrier from the first sector that crosses a TC area

However, please note sometimes two airlines who have interlining agreements may specifically exclude combination or where the Validating and/or the Transporting Carrier have Ticket Stock Restrictions. In such cases, please refer to the Fare Quote Notes of the desired fare.

I am not claiming to be the original author of anything- nor do I think I have touched all aspects of interlining and finally PLEASE dont PM me for more assistance on this topic- I am myself just learning so am not a Sensei:rolleyes:

Feel free to add- I hope for all the Elders understanding and hope not to have broken any laws of the board's Omerta:D