A suitcase’s journey: baggage conveyor systems, screening and loading

You are standing on the observation deck, and next to the long-haul jet a train of small trailers rolls up, loaded with silver containers. A loader lifts them one by one into the cargo hold, while the fuel truck is already waiting at the tail. What you are seeing is the last leg of a journey that began hours earlier at the check-in counter. This article explains baggage handling at the airport: how a suitcase finds its way through the conveyor system, security screening and sorting, why transfer baggage is so tricky and how loading works depending on the aircraft type.

Baggage handling: the short answer

At the departure airport, a checked suitcase essentially goes through five stations: at drop-off it gets a tag with a barcode, travels over the baggage conveyor system to checked baggage screening, is then automatically sorted by its barcode, collected at a make-up position for its flight and finally driven to the aircraft and loaded. At the destination airport the whole thing runs in reverse up to the baggage belt. When connecting, an intermediate leg is added in which the suitcase has to switch from one aircraft to the next within a short time.

Station 1: drop-off and bag tag

At the counter or the self bag drop, your suitcase is weighed and gets a baggage tag, known in industry jargon as a bag tag. Its core is the so-called license plate: a ten-digit number printed as a barcode and in plain text. It is defined in IATA Resolution 740. The number contains the airline’s three-digit numeric code and a six-digit serial number. The first digit reveals the type of tag:

• 0 – normal tag of an airline, also for baggage checked through across several airlines
• 1 – fallback tag generated by the airport’s baggage system itself when communication between the systems fails
• 2 – rush tag for suitcases that missed their flight and are being forwarded

At the same time, the airline’s check-in system sends a message to the baggage system: this passenger, this flight and, where applicable, these connecting flights belong to this number. From now on nobody has to “read” the suitcase anymore – the system decides based on the number alone. The barcode standard came about after the bombing of Air India Flight 182 in 1985; IATA introduced it as a standard in 1987. Some airlines and airports now add RFID chips in the tag, because radio labels can still be read even when the barcode is crumpled or dirty.

The tag also carries the IATA code of the destination airport in large letters, such as FRA or MUC. That is needed mainly by people: for manual sorting when a barcode is unreadable, and on the apron.

Station 2: the baggage conveyor system

Behind the counter, your suitcase disappears into a network of conveyor belts, diverters, inclines and spirals. How this network is built depends heavily on the size of the airport.

• Belt systems: Smaller airports work with classic conveyor belts. The suitcases ride directly on the belt, and diverters and pushers redirect them. Belts typically run at about 2 to 3 meters per second.
• Tote-based systems: Large hubs put the suitcase in its own tote. The tote carries an ID and is permanently assigned to the suitcase, which makes tracking much more reliable. Such systems reach top speeds of more than ten meters per second and bridge long distances between terminals far apart. Frankfurt Airport works with a tote system, as does Terminal 2 at Munich Airport. There the empty totes pick up the baggage of arriving passengers on their way back.
• Sorters: To distribute baggage to the individual flights, many systems use tilt-tray sorters, which tip the suitcase off to the side at the right spot, or cross-belt sorters with small transverse belts. Terminal 1 in Munich, for example, uses a tilt-tray sorter.

At several points, automatic scanners read the barcode, usually arranged in a ring around the belt so the position of the tag doesn’t matter. If that fails, the suitcase ends up at a manual coding station, where an employee reads the number and types it in.

The early bag storage

Anyone who checks in very early often drops off their suitcase hours before departure. So that these suitcases don’t clog the make-up positions, large systems have an early bag storage (EBS). There the suitcases park in racks or storage lanes until the system calls them up in good time before departure. Terminal 5 at London Heathrow, for example, can temporarily store up to 4,000 pieces of baggage this way.

Station 3: checked baggage screening

Before a suitcase may enter the cargo hold, it is X-rayed. The obligation comes from EU aviation security law, which is explained in detail in the article EU Regulation 300/2008 and Implementing Regulation 2015/1998. In Germany, Section 5 of the Aviation Security Act (Luftsicherheitsgesetz) provides that the aviation security authority may search, X-ray or otherwise inspect checked baggage; background is in the article The Aviation Security Act explained.

In modern systems, the screening is built into the conveyor line and typically runs in several stages:

After the attacks of September 11, 2001, full screening of checked baggage was made mandatory in many countries, including the EU and the US; how much the attacks changed aviation security overall is described in the article How 9/11 changed aviation security. If you are interested in the people behind the screens: the job is introduced in the article Becoming an aviation security assistant.

Station 4: sorting and baggage reconciliation

After clearance, the system reads the barcode again and directs the suitcase to its make-up position – in industry jargon also called a chute. That is a belt, a chute or a carousel where handlers stack the baggage of a flight by hand into containers or onto baggage carts. Many airlines load deliberately: suitcases with a priority tag go in last so that they come out first at the destination. Transfer baggage with a tight connection is often collected separately.

During loading, staff scan every suitcase. There are two reasons for this. First, IATA Resolution 753 requires its member airlines to track baggage at at least four points: when the passenger hands it over, when it is loaded onto the aircraft, when it is handed over to the transfer area and when it is returned to the passenger. Second, the scan serves baggage reconciliation: the system checks whether the associated passenger has actually boarded. If someone is missing, their suitcase generally has to come back out of the cargo hold. That is exactly why you sometimes hear the announcement that a departure is delayed because baggage is being offloaded – finding that one suitcase in the container costs valuable minutes.

Station 5: transport and loading

From the baggage basement, a baggage tractor pulls a chain of trailers (“dollies” for containers, open or covered baggage carts for loose baggage) across the apron to the parking position. Whether that is a gate with a passenger boarding bridge or a remote stand hardly matters for the baggage handlers – more in the article Gates, boarding bridges and remote stands. How loading then looks is decided mainly by the aircraft type.

Aircraft	Loading method	What you see at the aircraft
Boeing 737-800	loose (bulk)	belt loaders at the cargo doors, handlers stack suitcases in the cargo hold by hand
Airbus A320, A320neo, A321	loose or in flat AKH containers	depending on the airline, belt loaders or container loaders; an A320 takes up to seven AKH, an A321 up to ten
Airbus A350-900, Boeing 777-300ER	LD3 containers (AKE) and pallets	container loaders at the forward and aft cargo doors, dolly trains with containers; plus a bulk compartment for bulky items and last-minute baggage
Boeing 767-300ER	smaller LD2 containers	its own container size because of the narrower fuselage, an LD3 fits only with a loss of space

The LD3 (IATA code AKE) is the classic in the lower deck: about 4.5 cubic meters of volume, about 1.63 meters tall, with a beveled side that follows the curve of the fuselage. The containers fit all Airbus widebody jets as well as the Boeing 777 and 787. The A320 family uses a variant flattened to about 1.14 meters with about 3.7 cubic meters, the AKH.

Containers have a big advantage: they are packed in the baggage basement already, and at the aircraft it is only a matter of bringing them to cargo-door height with the loader and rolling them in. That saves time in the turnaround. Loose loading, by contrast, needs no expensive equipment and is proven on the short ground times of low-cost airlines, but means hard work in a cramped cargo hold. What this job looks like from the inside is described in the article Working on the apron.

Loading is not arbitrary: the load plan determines which container goes in which position, because weight and center of gravity are decisive for flight performance. Baggage also often shares the cargo hold with freight and mail. Only when all cargo doors are closed and the numbers add up does the pushback follow.

Transfer baggage: the trickiest leg

At the destination airport, baggage travels from the aircraft to the baggage belt – usually the uncomplicated part. It gets exciting when connecting. Then the suitcase generally has to get from the arriving aircraft through the transfer system, often through another security check, to the make-up position of the connecting flight within the minimum connection time. How airlines and airports set these times is explained in the article Connecting at a hub.

The statistics show why it is so tricky: according to IATA, around 41 percent of all mishandled bags arise during connections, and the IT service provider SITA cites a share of 39 percent in its 2025 baggage report. At hubs with wave operations, many aircraft land shortly after one another, and thousands of suitcases have to be redistributed at the same time. How these hub waves work and when they are worth it for spotting is in the article Understanding and using hub waves.

With very tight connections, some hubs also drive suitcases directly from aircraft to aircraft, without a detour via the system. That requires good advance information on which suitcases are affected.

When it goes wrong

Overall, baggage handling has become astonishingly reliable. According to IATA, 6.3 bags per 1,000 passengers were mishandled worldwide in 2024, about 33.4 million in total. Since the start of the baggage tracking initiative, the rate has fallen by about two thirds according to IATA. Most mishandled suitcases are merely delayed and follow on a later flight – then with a rush tag.

Two historical cases show how much depends on a working system:

• Denver, 1990s: The new airport was to get a fully automated baggage system. In tests the system showed massive problems, and the opening was postponed by 16 months to February 1995. The system was never reliably operated to its intended extent and was finally abandoned in September 2005.
• Heathrow Terminal 5, 2008: At the opening on March 27, 2008, IT errors and teething problems meant British Airways had to cancel more than 500 flights in the first ten days. About 42,000 suitcases did not travel with their owners during that time.

Both cases still have an effect today: new baggage systems are now tested for a long time in trial operation before they go live.

What you see of it as a spotter

As a spotter you don’t get to see the baggage basement, but you see all the more of the last leg. The boundary between public and secured areas is explained in the article Landside, airside, security area. From observation decks and hills you can watch the activity well:

• Dolly trains on the apron roads: They often reveal where a widebody jet is about to be handled. From the Zeppelinheim viewing platform or the Munich Airport visitors’ hill (Besucherhügel), you see parts of the apron depending on your viewing direction.
• Container loaders and belt loaders: They stand at the cargo doors and make a nice detail subject for turnaround series – especially with widebody jets with two loaders at once.
• The last minutes: If a cargo door is opened once more after the passenger doors have closed, there is often a late-loaded or offloaded suitcase behind it.
• Mistaking it for freight: Anyone who sees containers quickly thinks of cargo. How to reliably recognize real freighters is in the article Recognizing freighters.

You get even closer on apron tours, which many airports offer. What you may and may not photograph there is summarized in the article Airport tours and apron tours.

Conclusion

A suitcase’s journey is an interplay of data flow and mechanics: the number on the bag tag links it to passenger and flight, the conveyor system and sorter bring it to the right destination, the multi-stage screening ensures security, and on the apron people take over with tractors, dollies and loaders. The weak point remains connecting, where minutes decide between making the connection and a rush tag. The next time you see a dolly train roll across the apron, you know how much work is behind every container.