Who is responsible for severely delayed baggage on a codeshare?

IME always the operating carrier.

If you provide the ticketing carrier and the operating carrier, FTers may be able to give some advice.

Last operating carrier.

Flew:

YVRYYZ AC
YYZYUL AC
YULBRU AC
BRUKGL SN (Brussels Airlines on AC ticket/codeshare)

All paid J and am AC SE.

Luggage was left in BRU and next flight is 3.5 days away which is when they say it will arrive.

Not only all my clothing and toiletries but also my monopod and DSLR charger which were for safari happening prior to luggage arrival.

If you know that the baggage was lost in BRU, any complaints should be directed to SN IMO as it was the carrier which didn�t manage to get your luggage on the same flight you were on. You should also be entitled to some compensation under the EU regs. as SN is registered in the EU and the flight departed in the EU, usually you�re entitled to toiletries plus reasonable amount of clothing. (in case you don�t have delayed luggage insurance through your CC)

A 3.5 days delay is annoying indeed, but then again KGL isn�t exactly the most developed place with plenty of flights. I guess they could have put the luggage on a KLM flight to get it to you a little quicker, but not sure about SN�s policies regarding using another carrier in these kind of scenarios.

Who else but the last operating carrier.. unless the last operating carrier can confirm that they didn't even receive the checked baggage to lose in the first place..

So internally, the last operating carrier, would ensure that the previous operating carrier would be responsible.. I would imagine..

If checked though, I would think the IATA rule remains that you should direct your complaint to the last operating carrier no matter what.

The AC/SN codeshare arrangement is one that does not operate as efficiently or as effectively as other codeshares...."leaving" the bag in BRU for 3.5days confirms that. They act just like their SN heritage code predecessor...who once left a bag for a week in ORD when they had 5th freedom rights ORD-YUL-BRU, and it would have taken 2 days to ship it by bus if they didn't want to give it to AA... E-mail [email protected] and demand your fair share of compensation under EU regulations.

I agree..

and leave the carriers to sort out the mess..

Also if the flight is booked using a cc that has baggage insurance.. claim thru that.. might actually be more effective to get reimbursement for delayed baggage (24 hour rule)

Really? Seemed to be working well for me. I'm in BRU every other month. I don't connect much but I have arrived on severely delayed flights operated by 9W, AC, CO and UA, and only on AC have I seen (twice this year) SN staff waiting at the top of the jetway with newly-issued boarding passes and flight info for passengers who missed their connection. I don't know whether credit ought to go to AC or SN but I wish more airlines were this proactive in handling missed connections.
On the other hand, the only time my luggage and I didn't make it together into BRU was because AC loaded it on the wrong bin in YYZ.

report it to the last operating carrier. they will sort the issue out themselves

Finally got my luggage. SN wouldn't deliver to my hotel so I had to send a driver to get it ($50).