orbitmic

Nobody is suggesting that the airline has the right to define its own liability. The point is that the airline is responsible for the "damage" resulting from the delay. Off the top of my mind, courts typically interpret that as meaning that the damage corresponds to reasonable, actual and verifiable expenses which are directly incidental to the loss of the bag up to the amount you mention which is specifically the maximum liability and not an automatic right.

So for instance, in this case, there is indeed no doubt that if skis have been checked in and are delayed the airline will reimburse the rental cost for the missing period, but that again will be a fairly low amount - in most stations, you'll probably get the skis and shoes together for about £30-40 and that would include the shoes which may not be part of what the OP checked in.

You are absolutely right that the airline cannot fix their own liability below the ceilings specified by UM99. For instance, it would be illegal for an airline to say "I won't pay more than £100/day". If a passenger can demonstrate that an expense, higher than that, was reasonable, actual, verifiable, and incidental, the airline would not have a leg to stand on. For instance, this would easily be the case if the airline has not delivered the luggage containing a person's wedding dress and she is marrying that day, or if the person is off on the cruise and they have to buy black tie attire due to the dress code on the boat, etc.

Again, however, it doesn't mean that any expense up to the MC99 limit is necessarily reasonable if it does not correspond to an actual damage, and the reason why I'm insisting is not to be pedantic but because I think that your statement above could be misread by people as suggesting that as long as they send the airline a bill for up to £1200 for a delayed bag, the airline will have to pay. That would not be accurate.

For instance, specifically, if the OP or someone in a similar situation saw this and decided that he/she is going on a shopping spree in Milan to buy a new pair of top of the range skis for £1200 after theirs have been delayed for 24 hours and that the airline will have to pay, they will be in for a disappointment and any airline that I can think of will refuse considering that this is not a reasonable incidental expense. Instead, they will probably offer a small participation that would be sufficiently above the cost of ski rental for the period that occurred before the passenger was reunited with his/her skis (assuming no damage) to be deemed a reasonable evaluation of the damage caused by the delayed bag. The airline would have no hesitation to leave the passenger settling the rest of his/her own bill and go to Court if they are unhappy.

Incidentally, since you mention UM99, it is important to remind people that art 19 exonerates the airline if it can prove that it has taken all measures that could reasonably be required to avoid the damage and/or that it would have been impossible for them to avoid it. Thus, in cases where the bag delivery delay actually happens not as a result of handling issues but due to circumstances outside of the airline's control (and its contracted agents) there may not be any liability at all.