Not every bag makes it into the hold at the expected time. The most common exception is “flight cut-off”: airlines set a strict time after which no more bags are loaded. If your bag arrives after that cut-off (perhaps you were stuck at security or on another flight), it must be left behind – it becomes mishandled baggage and will arrive on a later flight, if possible.
Another exception is overweight/oog (out-of-gauge) baggage. Very heavy or oddly-shaped items sometimes can’t fit easily through the standard cargo doors or might violate aircraft limits. In those cases, the bag might be sent on a different flight (or on the same plane but through a cargo door, if available). This is planned during the check-in phase (the agent flags it in advance).
Re-route cases: If your itinerary changes (say you were rebooked or your flight was canceled), any checked bag must be retrieved and put on the new flight. This means it’s taken out of the original build and held until the alternative route.
International transfers: For some international transfers, bags might be transferred between planes in a secure area before reaching the final hold. For example, a bag on a U.S.-bound flight may need to go through additional scanning at the transfer airport. In such cases, it might be built to a short-term holding cart rather than loaded on the first aircraft.
In all exceptions, ground staff follow strict protocols. For example, if a bag is oversize, it will have been tagged for special loading (often via a different door). If a bag must be offloaded due to miss-checking or failed security, it is tracked as mishandled baggage (using irregularity codes) and stored securely until it can be reunited with you.
The key is that even when the normal build process changes, handlers ensure every bag is documented. This prevents mishaps like putting baggage on the wrong flight or leaving it on the tarmac unattended.
