Airlines are responsible for checking in and barcoding bags. BAA assumes responsibility the moment bags leave the scales. They are X-rayed for explosives. An infra-red scanner reads the barcodes and dispatches the bags along conveyor belts, automatically ejecting them when they reach the right chute. There, airline handlers load them on to the plane. BAA undertakes to deliver bags from check-in to chute within 12 minutes.

Bags get lost mostly while being transferred from incoming to outgoing flights. Airlines aim to unload bags within 25 minutes of planes landing. Their handlers take the bags to transfer docks where BAA takes over. They are screened, sorted and sent either to the appropriate chute within the same terminal, or by van or tunnel to another terminal where they are routed to the correct chute. There airline handlers are supposed to load them within 20 minutes. The recommended minimum time for transferring bags within a terminal is 60 minutes, and 75 minutes between terminals. It often takes much longer, which is why bags miss connecting flights.

Airline handlers unload all other bags arriving in Heathrow and put them on the short belts that lead to carousels (pictured here) in reclaim areas. Delays here are almost always because of slow unloading.

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