As many here know, I have posted in the past just how confusing the whole bag fees situation is when you're traveling on multiple carriers.
Specifically, currently AA's contracts don't specify
any rules about this; the
Conditions of Carriage and
International General Rules AA1 imposed on you are vague (the latter reads "In addition to the charges or fees included as part of the purchased fare(s) on the ticket, passengers on codeshare flights operated by another carrier may also be subject to charges and fees imposed by the operating codeshare carrier"), and the DOT has not forced the airlines to provide any clarity on this subject.
IATA Resolution 302, "Baggage Provisions Selection Criteria", is supposed to apply to
all tickets issued on or after 1 April 2011, and introduces the concept of the "Most Significant Carrier" (MSC) of the journey, indicating that
generally the allowances and fees of the MSC apply to the entire journey (i.e. entire ticket,
even if roundtrip).
The resolution is as follows:
unless otherwise agreed the following baggage provisions selection process should apply for interline journeys
1) Baggage provisions are defined as free baggage allowance rules and baggage charges
2) For the purposes of baggage provisions selection, the following 4 step process should
apply for interline journeys:
... a) Step 1: If the published baggage provisions among all participating carriers are the same; these provisions will apply.
... b) Step 2: Where the one or more published baggage provisions differ between participating carriers, apply any common provisions are where provisions differ the published baggage provisions of the Most Significant Carrier (MSC). (In case of code share flights this will be the Operating Carrier, unless that carrier publishes a rule stipulating that it will be the Marketing Carrier).
... c) Step 3: If the MSC does not publish baggage provisions for the journey concerned apply the published baggage provisions of the carrier accepting the baggage at check-in.
... d) Step 4: If the carrier accepting the baggage at check-in does not publish baggage provisions for the interline journey concerned apply the published baggage provisions of each operating airline sector-by-sector.
MOST SIGNIFICAN CARRIER (MSC)
3) the MSC is.
... a) For travel between two or more IATA areas, the carrier performing carriage on the first sector that crosses from one area to another.
Esception: IATA area 123 only, the carrier providing carriage on the first sector that crosses between IATA area 1 and IATA area 2.
... b) For travel between IATA Tariff sub-areas, the carrier performing carriage on the first sector that crosses from one sub-area to another.
... c) For travel within a IATA Tariff sub-areas, the carrier performing carriage on the first international sector.
It is unknown to me whether AA is implementing this effective 1 April 2011 as per IATA (we will see if they modify the tariffs) or if they have any automation to support it (they need to know the MSC's baggage allowances and fees at check-in and presumably do all the calculations automagically). Any information from AA's presence on FlyerTalk would be welcomed.
As a reminder, IATA defines the world into 3 areas (IATA area 1/2/3), and each area has sub-areas.
IATA Area1
North America/South America/Hawaii etc.
“IATA Tariff sub-area” of “IATA Area1”
North America (USA, Canada and Mexico)
Caribbean Islands
Central America
South America (Brazil, Chile, Peru etc.)
IATA Area2
Europe/Middle East etc.
“IATA Tariff sub-area” of “IATA Area2”
Europe
Middle East
Africa
IATA Area3
Japan/Korea/Thai/Singapore/Philippines/India/Guam etc.
“IATA Tariff sub-area” of “IATA Area3”
Japan/Korea (Japan and Korea)
South East Asia (China, Singapore, Thai, Vietnam, Guam etc.)
South India (India etc.)
South East Pacific (Australia, New Zealand etc.)
Sources: