Interline baggage transfer liability and proof standards

Strategic liability allocation and forensic evidence standards for resolving interline baggage transfer failures between commercial air carriers.

In the complex ecosystem of global aviation, the seamless transition of checked luggage between different airlines—known as interline baggage transfer—is a logistical marvel that frequently fails. When a suitcase vanishes or arrives damaged during a multi-carrier itinerary, passengers often find themselves caught in a “blame loop” between the operating carrier and the marketing carrier. The resolution of these disputes rarely depends on who lost the bag, but on who held the final contractual responsibility at the moment of the failure.

This topic turns messy primarily because of documentation gaps in the WorldTracer system and the lack of synchronized timestamps between ground handling agencies. Vague internal policies and inconsistent application of the Montreal Convention often lead to summary denials of claims. To move past the frustration of automated responses, parties must understand the hierarchy of proof—from the initial 13-digit ticket number to the final Property Irregularity Report (PIR)—and the specific legal triggers that pin liability on a specific carrier.

This article clarifies the standards of evidence required to successfully navigate baggage disputes, providing a workable forensic workflow for legal professionals and claims adjusters. We will explore the “Last Carrier” rule, the technical logic of interline traffic agreements, and the practical steps needed to preserve volatile digital evidence before it is purged from carrier servers.

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Time, cost, and documents:

• Notice Deadlines: 7 days for damage, 21 days for delay/loss under the Montreal Convention.
• Proof Package: Original baggage tag receipts, 13-digit E-ticket, PIR, and itemized purchase receipts for essentials.
• Recovery Ceilings: Approximately 1,288 Special Drawing Rights (SDR) per passenger for international itineraries.

Key takeaways that usually decide disputes:

• Contractual Privity: The marketing carrier may sell the ticket, but the operating carrier of the final segment usually handles the physical claim processing.
• Interline Integrity: Separate tickets purchased for “self-connecting” flights sever carrier liability for transfer failures.
• Reasonable Measures: Carriers must prove they utilized all available Baggage Reconciliation Systems (BRS) to prevent the loss to avoid strict liability.

Quick guide to Interline Baggage Liability

• The “Successive Carrier” Test: In multi-carrier journeys, any carrier that accepted the baggage without reservation is jointly and severally liable for damage.
• Scan Gap Analysis: Liability often shifts to the carrier that failed to perform the “Received” scan during the Interline Baggage Message (IBM) exchange.
• Interline Traffic Agreements (ITA): These behind-the-scenes contracts define reimbursement rates between airlines, often influencing the “generosity” of initial settlement offers.
• The 21-Day Threshold: A bag is legally “lost” (not just delayed) on day 22, triggering full depreciated value compensation requirements.

Understanding interline transfer failures in practice

The transition of baggage at a major hub is governed by IATA Resolution 780. When a passenger checks a bag at the origin, a 10-digit License Plate (barcode) is generated. This code is the only link between the bag and the passenger’s itinerary. In practice, disputes arise when Flight A arrives late at the hub. If the Minimum Connection Time (MCT) for baggage is 60 minutes and the flight arrives with only 40 minutes to spare, the baggage is “short-shipped.”

The dispute usually intensifies when the first carrier claims the bag was delivered to the interline belt, but the second carrier claims it was never received. This is where forensic scan data becomes the deciding factor. Unlike passengers, baggage does not have a “will” to move; every movement is the result of a physical scan or a mechanical sorter action. If the Baggage Source Message (BSM) was correctly transmitted but the Baggage Transfer Message (BTM) was not acknowledged, the liability remains with the delivering carrier.

Legal and practical angles that change the outcome

One of the most significant variables in these disputes is the distinction between Contracting Carriers and Actual Carriers. Under the Montreal Convention, a passenger has the right to take legal action against the first carrier, the last carrier, or the carrier that performed the carriage during which the loss happened. In practical terms, however, most airlines have agreed through Alliances (Star Alliance, Oneworld) that the “Last Carrier” will handle the administration of the claim. If the last carrier denies liability, they must provide scanned proof of non-delivery from their partner to successfully redirect the claimant.

Documentation quality is the pivot point. A passenger who leaves the airport without a PIR number has effectively created a presumption of safe delivery. While this presumption can be rebutted with photos or GPS tracker data (like AirTags), the carrier’s legal defense will immediately lean on the lack of an immediate report to argue the damage or loss occurred post-carriage. Therefore, the “Workable Path” always begins at the Baggage Service Office (BSO), not the customer service phone line.

Workable paths parties actually use to resolve this

Most interline disputes are resolved through a three-step escalation process. First, the informal tracing period (1-5 days), where the WorldTracer system attempts to match found bags with lost files. Second, the interim relief phase, where the last carrier provides a daily stipend or reimbursement for “essential items.” This is a critical tactical step; accepting this relief does not waive the right to full compensation for the bag itself.

If the bag remains lost after 21 days, the third phase is the valuation dispute. Carriers will often apply aggressive depreciation schedules (e.g., 10-20% per year). A successful strategy here involves providing original purchase receipts or bank statements to establish the “baseline value.” If the carrier refuses a reasonable settlement, the mediation or administrative route through national aviation authorities (like the DOT or CAA) is usually more effective than litigation, as regulators can access the confidential interline logs that passengers cannot.

Practical application of baggage audits in real cases

When a large-scale transfer failure occurs—such as a hub’s Baggage Handling System (BHS) outage—the airline’s priority is clearing the backlog, not documenting liability. To protect a legal position, one must follow a sequence that forces the carrier to acknowledge the chain of custody. This prevents the airline from later claiming the bag was “lost by the passenger” or “mis-tagged.”

1. Verify the PNR Integrity: Ensure all segments are on the same 13-digit ticket to establish through-carriage liability.
2. Issue the PIR Immediately: Do not accept “we will email it to you.” Demand the physical printout with the timestamp from the WorldTracer terminal.
3. Request the Scan History: Formally ask for the Baggage Tag History (BTH). This report shows every time the bag was scanned by a laser or RFID reader.
4. Analyze the “Received” Gap: If the BTH shows a scan at the Transfer Belt of the hub but no scan on the second aircraft, the liability is pinned to the second carrier.
5. Apply Depreciation Logic: Build an itemized list with ages and prices. Compare the carrier’s offer against the Montreal Convention liability limit (approx. $1,700 USD).
6. Document Mitigation Effort: Record all communications with the BSO. If the airline failed to update the WorldTracer file for 7 days, they have failed to take “reasonable measures.”

Technical details and relevant updates

Modern Baggage Reconciliation Systems (BRS) have introduced a higher standard of care. IATA Resolution 753 now requires carriers to track baggage at four key points: Check-in, Aircraft Loading, Transfer to another carrier, and Arrival. This digital trail has made the “missing bag” excuse much harder to sustain in court. If a carrier cannot produce the “Transfer” scan, they are effectively admitting to logistical negligence.

• RFID Integration: In hubs like ATL or LHR, Radio Frequency Identification provides a 99.9% accurate track of the bag’s location, making BTH reports nearly impossible to dispute.
• The Special Drawing Rights (SDR) Fluctuation: The liability limit is not in USD or Euros; it is in SDR, which fluctuates. Ensure the conversion rate is calculated for the date of the loss.
• Self-Service Kiosk Risks: If a passenger prints their own tag and it detaches, the airline may argue contributory negligence. Documentation must prove the tag was properly applied.
• Limited Release Tags: Be wary of carriers applying LRTs to fragile items; this does not exempt them from liability for gross negligence or loss, only for minor pre-existing damage.

Statistics and scenario reads

These figures represent operational realities in the interline baggage sector. They are monitoring signals used by risk officers to determine the likelihood of systemic transfer failure at specific hubs or between specific alliances.

Successive Carrier Liability Shifts:

• Initial Claim Success: 22% → 74% (Increase in resolution speed when original Baggage Tag Receipts are provided in the first demand).
• Valuation Settlements: 45% → 88% (Success rate of avoiding depreciation caps when three-year-old receipts are presented).
• Interim Relief Issuance: 12% → 65% (Increase in stipend availability when the PIR is filed within 60 minutes of landing).

Monitorable Performance Metrics:

• Short-Ship Rate: Target < 2.5 per 1,000 passengers for interline transfers.
• WorldTracer Update Latency: Target < 4 hours from bag identification to passenger notification.
• Scan Integrity Rate: Target > 99% for Transfer Point IBMs.

Practical examples of Interline baggage disputes

Common mistakes in interline baggage disputes

FAQ about interline baggage failures

References and next steps

• Immediately file a Property Irregularity Report (PIR) and secure the 10-character code.
• Preserve the physical baggage tag receipt; it is the “DNA” of your claim.
• Itemize all contents and gather purchase evidence (receipts/emails) within 48 hours.
• Submit a formal written claim to the last carrier’s legal or claims department within 7 days.

Related reading:

• Understanding Montreal Convention Article 17 and 22: Baggage Liability Limits
• IATA Resolution 780: Interline Baggage Standards for Succeeding Carriers
• How to Read a WorldTracer History Report: A Forensic Guide
• The Role of RFID and Resolution 753 in Modern Baggage Audits

Normative and case-law basis

The primary governing source for international baggage liability is the Montreal Convention 1999 (MC99), which establishes strict liability for baggage loss, damage, or delay during carriage by air. This treaty replaced the aging Warsaw Convention and standardized the Special Drawing Rights (SDR) as the universal currency for compensation. Domestically, carriers are also bound by their Contract of Carriage, which must be consistent with national DOT or CAA regulations regarding consumer protection.

Case law such as Stott v. Thomas Cook and various ECJ rulings have clarified that the “carriage by air” includes the period the bag is in the charge of the carrier, even on the ground. These precedents emphasize that interline agreements do not relieve the last carrier of their duty to the passenger, as established in the Successive Carriage clauses of the Montreal Convention.

Authority Citations:
International Air Transport Association (IATA): iata.org
International Civil Aviation Organization (ICAO): icao.int

Final considerations

In the world of aviation liability, a missing bag is not an accident; it is a breakdown in a multi-billion dollar data chain. Success in these disputes is rarely won by the passenger who is the loudest, but by the one who is the most meticulously documented. By understanding that the “last carrier” is the legal guardian of the journey, you can bypass the administrative denials and force a resolution based on established treaty law.

As Resolution 753 becomes the industry standard in 2026, the era of “we don’t know where the bag is” is ending. Every transfer is now a verifiable data point. Parties should focus on audit-ready evidence and clear, itemized valuations to ensure that when the interline system fails, the legal recovery system works exactly as intended.

This content is for informational purposes only and does not replace individualized legal analysis by a licensed attorney or qualified professional.