The entity that was initially responsible for the transport of the cargo is the party liable for the loss of the cargo. Earlier in the thread, it was mentioned that this was a TD Bank shipment. If so, the bank's Financial Institution Blanket Bond Form 24 aka Comprehensive Crime insurance policy will pay first. It is highly likely that the bank was retaining the ultimate requirement to insure the property during the transit. If the bank insurers pay, they would then subrogate against the parties contracted to transport the gold. Depending upon the contracts used, the liability for the loss may have been assumed in whole or in part by the contracted armoured company and/or the air cargo carrier . If the armoured car company contracted with Air Canada cargo (assuming it wasn't TD bank that did so), there would have been a cargo transport agreement. Unless there is a specific instruction and contractual requirement otherwise, it is conceivable that Air Canada would attempt to limit its liability to the amounts set out in their international cargo contract of carriage. I think it is something like $1.0/kilo or 22 SDR/kilo (A higher limit can apply depending upon the cargo classification).
That's a lot of ifs and subjectivities. And one big condition is that if the contract of carriage included the warehouse storage, then the limitations of the various international air conventions still apply. Another big if is how the loss will be subrogated. The indemnifying insurers could seek to squash the limitations of the cargo contact of carriage by showing that there was “willful misconduct”. The Hague Protocol defines Wilful Misconduct as an intent to cause damage or acting recklessly and with knowledge that damage would probably result. The easy access of thieves to the cargo and the absence of basic loss prevention controls suggests that Air Canada was negligent and should have expected a loss to ensue. I expect that the lawyers would be looking at past thefts and calling up the airline's internal audits to determine if there were outstanding loss prevention recommendations. If they can establish that the airline knew there was an exposure and did not act accodingly, the settlement could be expensive for the airline.

The use of the term bond refers to a time when coverage was issued solely on the exposure of "Employee Dishonesty". Coverage is now issued on a Comprehensive Crime basis. If Air Canada is liable for some or all of the loss, its crime insurance would need to have two important insuring agreements; The definition of insured property would have to include valuable metals like gold and there would need to be an extension for loss of customer property while in the care, control and custody of the insured. Even though this is a liability exposure, a liability insurance contract excludes loss due to employee dishonesty. It is the Crime policy that pays. (And it is not paid as an employee dishonesty claim.)