How Airport Baggage Handling Systems Work

The Journey Begins: Check-In to Sortation

The moment a passenger checks in a bag, it enters one of the most sophisticated automated logistics systems in existence. After tagging (either by an agent or at a self-service kiosk), the bag moves onto the in-line baggage system — a network of conveyor belts running through the airport's infrastructure, hidden largely from public view. At major hub airports, this system spans dozens of kilometers and can process thousands of bags per hour continuously.

The first critical process is security screening. In the United States, every checked bag must pass through Explosives Detection System (EDS) equipment — large Computed Tomography (CT) scanners similar to medical CT machines but optimized for luggage. These machines create a three-dimensional image of bag contents and analyze the density and shape of objects, automatically flagging anything that resembles a threat. Bags that clear automatically (the vast majority) are routed onward. Flagged bags are diverted to manual screening stations where security officers physically examine the contents. The entire automated screening process takes under 30 seconds per bag.

After security clearance, bags enter the sortation system. Optical barcode scanners or RFID readers positioned at key points in the conveyor network read the luggage tag and route the bag toward its destination carousel or transfer point. At modern airports, the sortation system is controlled by a Baggage Handling System (BHS) — a central computer that tracks every bag's location in real time, knows each flight's departure time, and makes routing decisions to ensure every bag reaches its outbound aircraft with time to spare. The system adjusts dynamically as flights gate-change or delay, rerouting bags in progress without human intervention.

The Technology Behind Baggage Tracking

Traditional barcode-based baggage tracking has inherent limitations. A barcode can only be read when a scanner has direct line of sight to the tag, and tags can be obscured by other bags, folded over, or simply missed. Typical barcode read rates in early systems were 85–90%, meaning 10–15% of bags passed through a scanner without being positively identified. This leads to misrouting and delayed bags. The solution that has transformed baggage handling is RFID — Radio Frequency Identification.

RFID baggage tags contain a small microchip and antenna that respond to radio-frequency interrogation without requiring line of sight. RFID readers can read tags through bags, at range, and even read multiple tags simultaneously in high-speed conveyor environments. When Delta Air Lines completed its RFID bag tracking deployment across its US network in 2016 — a $50 million investment — bag tracking accuracy improved from approximately 90% to 99.9%. Lost bag rates fell dramatically. The IATA Resolution 753 (effective 2018) now requires airlines to track bags at four mandatory points: at check-in, loading, transfer, and arrivals. Most major carriers are implementing RFID systems to meet this standard efficiently.

Airlines have extended bag tracking to passenger-facing apps. United, Delta, Alaska, and many international carriers now push notifications to the airline app when your bag is checked in, when it is loaded onto the aircraft, when it has arrived in baggage claim, and — in the case of misrouted bags — to explain where it has gone and when it will be delivered. This transparency has significantly reduced customer service calls and improved satisfaction even in the (rare) cases when a bag is delayed. Some airlines have integrated Apple AirTag integration into their apps, and IATA has been developing standards for passenger-side bag tracking through personal tracking devices.

Sortation Carousels and Early Bag Storage

Large international airports with significant hubbing operations must handle bags that arrive hours before their connecting or originating flights. Storing hundreds of thousands of bags efficiently requires sophisticated Early Baggage Storage (EBS) systems — automated warehouses within the airport where bags can be held, retrieved on demand, and injected back into the BHS precisely when needed. Munich Airport's baggage system includes extensive EBS that can store thousands of bags and retrieve any specific bag within minutes for late check-in passengers or rerouted connections.

Tilt-tray sorters are the workhorses of high-capacity baggage sortation. These systems consist of thousands of individual platforms (trays), each carrying a single bag, moving continuously on a loop at up to 30 km/h. Centralized sortation computers trigger individual trays to tilt at precisely the right moment to slide each bag into the correct chute leading to its departure flight's makeup area. Large hub airports like Amsterdam Schiphol and Frankfurt use multiple parallel tilt-tray systems. Frankfurt's system spans over 60 kilometers and processes up to 21,000 bags per hour through 26 sorting destinations — an engineering system comparable in complexity to a city's metro network.

At the departure gate, bags arrive via conveyor to a makeup area where airline ground handlers load them into Unit Load Devices (ULDs) — standardized aluminum containers or pallets that fit into the aircraft hold. Efficient ULD loading maximizes hold utilization and ensures weight is distributed within the aircraft's center of gravity limits. The loadmaster (usually the airline's load planning system, with final verification by a human) produces a load sheet specifying exactly where each ULD is positioned in the hold, what it weighs, and how its placement affects the aircraft's trim. This information is provided to the flight crew and affects takeoff calculations.

When Bags Go Wrong: Mishandling and Recovery

Despite the sophistication of modern BHS, bags still occasionally miss flights. The most common cause is insufficient connection time — a passenger with a 45-minute connection at a large hub may clear the aircraft in time, but their bag may not be unloaded, transported to the transfer conveyor, sorted, and loaded onto the outbound flight in that window, particularly if the inbound flight arrives late. Airlines publish minimum connection times (MCTs) — the shortest layover for which the airline guarantees to transport both passenger and bag to a connecting flight — and MCTs for bags are typically longer than for passengers in self-transfer scenarios.

When a bag is confirmed to have not been loaded (via the real-time RFID tracking system), the airline's World Tracer system (the industry-standard global bag tracing database, maintained by SITA) creates a file that automatically tracks the bag through subsequent flights and matches it to its owner. Most mishandled bags are reunited with their owners within 24–48 hours via delivery to the passenger's destination address — an arrangement that, while inconvenient, requires the airline to pay for baggage delivery and in many jurisdictions to compensate the passenger for reasonable expenses incurred during the delay.

The rate of mishandled bags — defined as delayed, damaged, lost, or pilfered — has fallen from 18.88 per 1,000 passengers in 2007 to 3.89 per 1,000 in 2023 according to SITA's annual Baggage IT Insights report. Permanent bag loss (bags that are never returned) is now extremely rare — less than 0.1 per 1,000 passengers — thanks to RFID tracking and global trace systems. When a bag is genuinely lost, Montreal Convention Article 22 limits airline liability to approximately $1,750 USD for international flights (Special Drawing Rights 1,288), though passengers with particularly valuable contents should declare them at check-in and pay an excess valuation fee for higher coverage.