As to the issue of "who" was the party who handled it.. Under convention it largely does not matter if the bag was handled by; thus "lost" by a 3rd party like Swissport.. The two conventions don't allow the carriers to shift that burden-- for LOST bags-- from themselves to the assigned 3rd party who may or may not have been an appointed handler at some point in the process.
Unlike LOST baggage rules, the rules for DAMAGED baggage DOES allow more exceptions for situations that occur while outside of the carriers control, as well as damage due to others baggage, as well as parts for bags are excluded (wheels) etc., etc..
As an insight-- its not uncommon for the airlines to have some form of a performance agreement or scope clause in their service agreement with these 3rd ground handling parties-- like Swissport-- that addresses this.. but that would take place only between the airline and their 3rd party *after* the claim is paid. Then the two parties would dissect what happened and then from there decide who pays what percentage of the passenger payment relative to the terms of their service agreement.
The only real exception to this issue of lost bag payment is IF your bag was properly and legally SEIZED or otherwise by a recognized governmental agency (like airport security or customs agents) or was destroyed due to having prohibited materials inside or represented a safety or security hazard to either airport, employee, airline or operational safety.. But both these scenarios are very, very infrequent in occurrence.
"Could you please point me in the right direction to find out about the International travel agreements. "
Assuming your travel is INTERNATIONAL in nature (to include domestic sectors of an international booking) then in order to know what "convention" applies, you have to know your origin country and destination country,
**IF** BOTH the origin AND destination ARE signatories to the newer Montreal Convention, then that convention would apply.
IF either, or both the origin and destination country are NOT signatories to Montreal, then by default, the older Warsaw Convention applies.
Both conventions use a bags recorded WEIGHT (not passengers assumed value) to determine the payment amount.
The older Warsaw is much less generous and is fixed at US$20 per KILO or baggage weight-- and again, is REGARDLESS of what was inside the bag or not.. So 10kgs of dirt gets paid out at the same level as 10kgs of fine silks..
If no official record of the bags weight exists, it is assumed to be the maximum allowed under your tickets allowance without the payment of excess charges.
If the newer MONTREAL Convention applies then the payment is a bit more complex but still is WEIGHT based and NOT value based.. the payment is made in what's called SDR's (or Special Drawing Right) which is a weighted IMF-calculated non-currency that takes into account several major currencies; and then is converted into any real currency at the then-quoted exchange rates.
The maximum payment under Montreal tends to be MUCH, much higher than under Warsaw, and the Montreal convention also has language to allow for the maximum payment amount to rise in line with inflation rates over time (based on language found in the convention itself), where as Warsaw does not allow for this; and therefore has been fixed at US$20/kg since inception.
Here is the most current list I can find of all the countries that have adopted and formally signed/ratified the newer Montreal Convention:
So, in order...
#1) You need to know what is/was the RECORDED weight of the bag... as that is what will be used to calculate payment-- not what was inside nor its value.
#2) You need to know if BOTH the origin AND destination countries on your trip are signatories to Montreal., If they are, then those rules and compensation schedule applies.. If one or both are NOT, then the older Montreal applies.
Once you know these issues, then I'd mail a claim letter to the carrier citing the appropriate international convention with copies of the Property Irregularity Report (PIR) which you (I assume) filed timely with the carrier when your bag didn't show up.
In most cases before they''ll pay you, you'll need to give them some paperwork, ticket proof, PIR copies, etc... and sign a Release and Discharge Agreement.
Edited: 19 August 2012, 2:05