Interlining, that is multiple carrier journeys, is similar to codeshare journeys and many of the same rules apply (Resolution 302 – see the Wiki on
Checked baggage allowance for details).
What is my baggage allowance?
The IATA rules use the same Resolution 302 rules as described in the Wiki on
Checked baggage allowance. The Most Significant Carrier rules apply but where a carrier has different baggage allowances for different sectors the Most Significant Carrier rules are supplemented by similar Sector rules. Using the Resolution 302 rules find the Most Significant Sector of the most significant carrier and you have your baggage allowance.
Remember that unlike codeshare it is the Operating carrier not the Marketing carrier that is to be used.
Even though it is now outdated looking at
http://www.frugalhack.me/2015/03/27/...w-to-use-them/
you can read “You’ll need to make sure the weights and sizes follow every airline’s rules that you plan on interlining the baggage to.” This is from early 2015 and IATA have changed the rules since then. But it is still worth thinking about especially if the journey involves a carrier with no free baggage allowance since no free baggage allowance appears to be a weakness in IATA Resolution 302.
Who interlines with who?
KVS publish lists of airlines that interline. An example for UA is shown below. Note this list is just an example and is about three years old and will have changed since then.
ELECTRONIC INTERLINE CARRIER AGREEMENTS-UA
INTERLINE CARRIER CODES
AA - AB - AC - AF - AH - AI - AM - AR - AS - AV
AX - AY - AZ - A3 - A9 - BA - BD - BE - BI - BR
BT - BW - CA - CI - CM - CO - CX - CZ - C5 - DL
EH - EI - EK - EL - EN - ET - EV - EY - FB - FI
FJ - FM - FV - FW - FZ - F9 - GA - GF - G3 - G7
HA - HU - HX - IB - IQ - JJ - JL - JP - JQ - J2
KA - KC - KE - KF - KL - KM - KQ - KS - KU - KX
LA - LG - LH - LO - LP - LR - LW - LX - LY - MD
ME - MF - MH - MI - MK - MQ - MS - MU - NH - NQ
NU - NZ - OA - OH - OK - OM - OO - OS - OU - OZ
PG - PK - PR - PS - PX - PZ - QF - QR - QX - RJ
RO - SA - SK - SN - SQ - SU - SV - S2 - S5 - S7
TA - TG - TK - TP - T0 - UL - UN - UO - UP - US
UX - VA - VK - VN - VS - VW - WF - WM - WP - WS
WY - XE - XF - XJ - XL - ZH - ZK - ZW - 2V - 3M
4C - 4M - 4Q - 7H - 9E - 9K - 9L - 9W
Oneworld changed its interlining rules this year and airlines are no longer required to interline baggage on separate reservations. Note that it is not forbidden to interline across reservations but it is no longer given that it will be done. Within a reservation it should always be done.
What if I cannot interline my baggage?
If through checking of baggage is not possible then it needs to be checked in again at some point of the journey. This usually requires that you go through the usual arrival procedures, collect your bags and check-in again. And this in spite of the fact that you already have your onward boarding pass! In some airports the transfer desk can retrieve and relabel your luggage. (DOH, CMB and sometimes BKK). There are probably many more but I do not know which
(Under development – more to come – your suggestions welcome.)