corporate-wage-slave

The key issue here is that for security reasons, every single bag on board needs to be security scanned with a passenger attached to it - or has been through an enhanced security process with a closed loop in terms of delivery to the aircraft.

The baggage identification issue relates not to the biometrics but to normal FLY or any similar system, where people are recorded as boarded - and therefore technically could get on the aircraft - but then don't appear to be onboard during reconciliation. One common problem is that some passengers become unwell, and elect / get elected not to fly. In some cases it isn't necessary for them to have stepped on board, but if the computer thinks it could have happened then the bags need to be reconciled. Bags in the hold also need to be reconciled. There are also the usual glitches that can happen when someone (e..g.) two boarding passes, the second gets failed and there is a debate as to what happened when. Also occasionally there are FLY outages, people check in during or before the outage, and then FLY doesn't really know who is on board or not. The latter is usually resolved during the boarding process.

In extreme circumstances, and I've only had this once in all my travels, the entire aircraft gets offloaded, people get taken down with their hand luggage to the apron/ramp , the empty aircraft checked by crew, and then asked to point to their hold bags before reboarding. At Heathrow you really want to avoid this if possible.