Originally Posted by LondonAussie

Need some advice please and sorry if there’s a lost luggage help megathread - mods please merge in.

My luggage is in Copenhagen airport, the flight left without it. 2 days ago. It wasn’t loaded on to the flight. BA says it hasn’t been located yet. I have an AirTag inside it and it’s actively updating. It’s in the terminal right next to a place on the map labelled Menzies Aviation Baggage Services. It hasn’t moved in 2 days. Maybe BA can fly me back there to find it and retrieve it myself?

But in all seriousness, what should my next steps be?

Originally Posted by 13901

I think, based on experience having worked in Baggage-related projects for a few years, that these devices will be next to useless in terms of finding bags, for a number of reasons. Firstly, many Baggage Handling Systems - such as T5 - are buried deep under a lot of concrete and steel. Trials using radio-emitting beacons have proved that, unless there are repeaters of some sort nearby, their range is very limited.

Then there is a fundamental difference between bags being "lost" and bags being "short-shipped". The latter is what happens in the majority of cases when you arrive at destination and bag isn't there. The airline has visibility of where the bag is; they're just pretty rubbish at telling people (and their own employees). Out of a 1,000,000 bags that fly on a good airline, approximately 5,000 will not make it to their destination at the same time as their owner. Out of these 5,000, between 4,900 and 4,950 are bags that got stuck in the system: most will have missed their connection, some actually got stuck on some conveyor, some had contents that required inspection and then there was no time to load them, some were bags left behind when the plane was full and yadda yadda yadda. The key here is the airline has information on their whereabouts, usually quite accurate. It just has varying degrees of success in sharing that info with its people and its customers, as well as getting that bag on its way to where it needs to be.

A bag in its journey through T5 gets scanned tens, sometimes hundreds, of times. So they're never 'lost'. A bag tracker, in this case, isn't really useful. We did some trials and, besides those that simply didn't work or reported the bag as being on the runway while it was on an arrivals belt in T5, even if it said "hey, the bag is in this corner of T5"... It wouldn't really say anything as there could be up to 5 levels of belt conveyors, trays and other machinery stacked one on top of another in that place. And I can simply access HAL's tools and see where the bag was scanned last, knowing that it'll be nearby.

A minuscule proportion (as I said, roughly between 100 and 50 bags per 1,000,000) are bags that simply disappear (their tag is ripped off and they have no recognisable traits, or they are nicked, or the bag courier leaves it on the kerb and so on). In this case, no one at the airline has the foggiest about the bag's whereabouts. This is the situation where a bag tracker would come handy but... will it still be charged? Will it be in range? Will it be accurate?

Originally Posted by 13901

I can provide an explanation of how an integrated baggage system works and why and how it might malfunction, plus a brief explanation of how the reflighting (getting your bags back) works.

I'd start with the caveat that the AirTags are not a useful tracking tool. They are a Bluetooth device that leverages on other iDevices with Bluetooth on, thus "pinging" their location with a margin of accuracy that can be of many tens of metres. In a place like the T3 Integrated Baggage system (T3IB for short) there will be no people, and thus no iDevices, in the overwhelming majority of the structure. Bottom line, you can't act on the information that the bag is somewhere because the AirTag says so.

Having said this, the journey of a bag at LHR is: input point (direct or transfer), security X-ray, Early Bag Store (if the bins for the flight aren't being filled yet), then down to the lateral, into the bin, onto the plane. During its journey, a bag is constantly scanned by readers (up to 20 times) Each scan generate a datum point: time & location of the bag. These records are then input in the Heathrow's Baggage Tracking System (back in the day it was called Merlin) and in the Baggage Reconciliation System (that the airline uses). One key (and confusing) thing to remember is that there's no centralised "database" for BA as an airline to collect all the baggage info into a single location. In other words, there is still no way for BA to log in somewhere and say "Hey, MrGB's bag has been scanned in Houston". Houston knows, but that message doesn't flow any further (yet). So when you arrive at your destination and your bag isn't there, the BA Handler only has the local info, or what is input in (yet another system) Worldtracer.
This isn't the case for some airlines. Delta, for instance, has end-to-end visibility in their entire network. BA should've had too, but Covid put a spanner in the works.

Now, why do bags miss? First, it's worth saying that the number of bags that don't make it is exceedingly low. The numbers are expressed in bags/1,000 passengers, but you can also do a gross %. IATA airlines, at an average, deliver bags together with their customers in 98-99% of cases (from memory). For those who don't make it, the main causes are, in order of likelihood:

1) Transfer bags taking too long to move from one flight to another - due to delay of the inbound, or something like that
2) Bags failing the security check, and thus requiring checks by hand - that takes time, bags misses flight
3) Human error; in the case of out-of-gauge items that can't travel down the automated way, the procedure is more human-centric and thus subject to error. Plus there can be egregious examples of stupidity, of which I've seen many over the years.
4) Outage
5) Weird occurrences, like "multi-reads": the system reads two different barcodes on the bag - you've left a stub there, for instance - and that barcode has been seen by the system in the recent (2-3 days) past. That'll confuse it, triggering a need for manual check. Other weird occurrences are two small bags ending on the same tray (the little wagons on which they travel), bag tags being ripped out, this sort of stuff.

Overall I'd say that, of bags that miss, 1) accounts for 70% of the total, 2) for 10% and the other 3 share the remainder. I'm not too sure about which scenario applies for yours, or why one appears to have gone in LYS.

Finally in my spiel, how do bags get reflighted? In outstations, where things are simpler, a bag is "found" by an employee and delivered to the appropriate airline, whose employees will handle the re-flight. In LHR, a bag that is "in-system" (i.e. not lying around) will, next time that is scanned, trigger an alarm and the reconciliation system will automatically re-flight. In other words, if BA123 to Timbuctu has departed and one bag is left behind (say stuck at security) the next time it's going to be scanned the system will go "hmm, BA123 has departed. This bag will need to fly on the next one to Timbuctu which is... BA123 of tomorrow". A new overlay bag tag will be printed and added by a worker, and the bag will go back and await its next flight. I've seen plenty of bags missing the first LIN flight and getting on the second one, for instance. Then it's down to the courier, which is usually the weak link of the whole thing. For some reason, courier companies range between the barely decent and the downright criminal.