The 30-Day/10-Day Rule: How the IATA Interline Traffic Agreement Dictates Lost Luggage Compensation

Every year, roughly 5.5 million checked bags are mishandled on multi-airline itineraries—a volume that would fill a standard Boeing 777 cargo hold 15,000 times over. When one of those bags vanishes on a journey involving three different carriers, the passenger is rarely forced to investigate which specific airline lost it. Instead, a strict back-office framework known as the International Air Transport Association (IATA) Interline Traffic Agreement dictates exactly who pays the passenger and how the airlines settle the bill among themselves. This invisible bureaucracy ensures that the financial friction of a lost suitcase remains a corporate problem, shielding the consumer from endless runarounds and jurisdictional disputes.

The foundation of this system is the "Last Carrier Rule," codified under IATA Resolution 780. As the U.S. Bureau of Transportation Statistics explicitly notes in its reporting guidelines, "Under IATA resolution 780, the carrier that operates the last flight segment generally accepts a mishandled baggage claim as reported by the passenger." When a traveler flies from Chicago to London on American Airlines and connects to Rome on British Airways, the final operating carrier—British Airways, in this case—is legally obligated to process the claim. The passenger files the Property Irregularity Report (PIR) at their final destination, and that final airline becomes the single point of contact, regardless of where the bag actually fell off the belt.[2]

This mechanism shields consumers from corporate finger-pointing. Under the Montreal Convention, an international treaty governing air carrier liability, passengers are entitled to compensation up to 1,288 Special Drawing Rights (approximately $1,700) for lost or delayed luggage. The final carrier must evaluate the receipts, determine the depreciated value of the lost items, and issue the payout directly to the passenger. They cannot delay the passenger's compensation by blaming the originating airline, nor can they force the traveler to file a secondary claim with the carrier that actually loaded the bag. The passenger is made whole by the airline that delivered them to their destination.

Once the passenger is made whole, the financial liability shifts to the back office, triggering the 30-day/10-day proration rule. The airline that paid the claim—known in IATA parlance as the Claim Receiving Airline—compiles the settlement documents and submits a prorated bill to the other carriers involved in the itinerary. Under standard IATA clearing house procedures, the receiving airline has exactly 30 days from the date of the passenger's payout to issue this internal invoice. This strict timeline prevents legacy claims from piling up and forces airlines to maintain efficient accounting practices when dealing with interline partners.

The burden of proof then falls entirely on the connecting airlines. When the billed carrier receives the invoice, they have a strict 10-day window to dispute the charge. To successfully reject the bill, they must provide definitive tracking evidence—such as a License Plate Number (LPN) scan mandated by IATA Resolution 753—proving they successfully handed the bag over to the next carrier. If they fail to produce this evidence within 10 days, they automatically accept their portion of the liability, and the funds are transferred through the centralized clearing house without further debate.

When fault cannot be definitively proven by barcode scans, the airlines fall back on a mileage-based proration formula. If a bag simply vanishes between a 4,000-mile transatlantic flight and a 500-mile regional connection, the compensation cost is divided proportionally based on the distance each airline flew the passenger. The long-haul carrier absorbs the vast majority of the financial hit, even if the regional carrier was the one that actually misplaced the luggage. This default mechanism ensures that claims are settled quickly, rather than languishing in endless investigations over a single missing suitcase.

The implementation of IATA Resolution 753 in 2018 fundamentally altered how these 10-day disputes play out. Before mandatory cross-industry tracking, airlines frequently relied on the default mileage proration because neither carrier could definitively prove where the bag was lost. Today, the resolution requires airlines to track baggage at four specific points: passenger handover, loading onto the aircraft, delivery to the transfer area, and return to the passenger. This digital chain of custody has transformed the proration process from a gentleman's agreement into a hard data exchange.

This tracking data serves as the ultimate arbiter in back-office disputes. If the first carrier scans the bag into the transfer system, but the second carrier never scans it onto the connecting flight, the digital trail establishes absolute fault. When the 30-day invoice arrives, the at-fault carrier has no grounds to initiate a 10-day dispute, and the cost is assigned entirely to them rather than split by mileage. Consequently, airlines have heavily incentivized their ground handlers to ensure every bag is scanned at every transition point.

Despite these clear frameworks, the system still encounters severe friction during mass disruption events. When severe weather or a global IT outage forces thousands of bags into the interline tracing system simultaneously, the sheer volume of claims can overwhelm the Claim Receiving Airlines. While the passenger-facing Montreal Convention allows travelers up to 21 days to declare a bag officially lost, the back-office settlement process can drag on for months as airlines negotiate bulk settlements outside the standard 30-day/10-day windows to clear the backlog.

The U.S. Department of Transportation (DOT) has also layered its own regulations over this international framework. For domestic flights, the DOT sets the liability limit higher, at $3,800 per passenger, and mandates that airlines refund any checked baggage fees if a bag is significantly delayed. However, the DOT explicitly recognizes the IATA Resolution 780 framework, affirming that the last operating carrier remains responsible for reporting and handling the mishandled baggage claim, even under federal scrutiny. This ensures that domestic and international rules do not conflict at the baggage carousel.[1][3]

The 30-day/10-day rule represents a rare alignment of consumer protection and corporate efficiency. By decoupling the passenger's compensation from the airlines' internal fault-finding process, the aviation industry ensures that travelers are not held hostage by inter-carrier disputes. The next time a suitcase fails to appear on the carousel after a multi-airline journey, the passenger can file their claim knowing that the final carrier is bound by an international agreement to pay first and ask questions later.