http://www.iata.org/pressroom/facts_figures/fact_sheets/Pages/abr-reso-302.aspxThis mostly involves baggage allowances and charges. If you are traveling on 1 airline it will not affect you (that airline rules will apply) - this will mostly affect people who are traveling on an interline journey.
This is the new resolution introduced by International Air Transport Association (IATA) for all member airlines in deciding baggage allowance and excess baggage charges for journeys involving multiple carriers. Baggage travel allowances and charges for travel involving more than one carrier will follow the allowances and charges of the "Most Significant Carrier" (MSC) of the journey.
First the IATA divided he regions into 3 Tariff Areas & sub Areas:
IATA Tariff Areas Area 1:
North America, Central and South America, Hawaii Sub areas 1. USA, Canada, Mexico
2. Caribbean
3. Central America
4. South America
Area 2:
Europe, Middle East Sub areas 1. Europe
2. Middle East
3. Africa
Area 3: A
sia, Guam, Southwest Pacific Sub areas 1. Japan, Korea
2. Southeast Asia
3. South Asian Subcontinent
4. Southwest Pacific
It is a bit complicated but here are a few examples of the MSC for travel between & within the 3 Tariff Areas::
Most Significant Carrier (MSC):
Example #1:
~The first carrier crossing the IATA Tariff Area (for travel across one Tariff Area).For travel from Japan to London -
Travel between Tariff area 3 to Tariff area 2:
Sector IATA Tariff Area CarrierJapan - Hong Kong Tariff Area 3 to Tariff Area 3 Qantas
Hong Kong - London Tariff Area 3 to Tariff Area 2 Cathay Pacific
Cathay is the MSC as they are the first carrier crossing the Tariff Area. (Qantas travel is from area 3 to area 3 -while CX is from area 3 to area 2).
~The first carrier crossing the IATA Sub-area (for travel within a Tariff Area). Example Sydney to HK - Travel within Tariff Area 3
Sector IATA Sub Area CarrierSydney - Singapore Southwest Pacific to Southeast Asia Qantas
Singapore - Hong Kong Southeast Asia to Southeast Asia Singapore Airlines.
Qantas is the MSC as they are the first carrier crossing the IATA Sub-area ~ so Qantas luggage rules applies for travel on both airlines.
~The first carrier flying an international sector (for travel within a Sub Area).Example from NYC to Mexico City - All travel in Area 1 & Sub Area 1.
Sector CarrierNYC - DFW American Airlines
DFW - Mexico City JetBlue.
JetBlue is the MSC as they are the first carrier flying an international sector (AA is domestic) ~ so JetBlue luggage rules applies for travel on both airlines.
Or from Thailand to HK
Sector CarrierPhuket - Bangkok Thai Airways
Bangkok - Hong Kong Dragon Air
Dragon Air is the Most Significant Carrier - they are flying the international sector.
This is a sh***y rule as if the majority of your travel is on carrier X that offers free checked luggage (while carrier Y doesn't) but carrier X is not the MSC then you will have to follow carrier Y luggage rules.
Now, how many airlines will follow the MSC approach. BA is of the airlines that "might" continue to apply their existing rule of first operating carrier.