The 45-minute checked bag rule is a strict deadline used by most major U.S. airlines—including Delta, United, and American—for domestic flights. It mandates that all checked luggage must be processed and dropped off at the ticket counter or bag drop kiosk at least 45 minutes before the scheduled departure time. If you arrive at the counter 44 minutes before your flight, the airline has the right to refuse your bags, as there is often not enough time for the automated belt system and ground handlers to get the luggage through security and onto the aircraft. For certain busy airports like JFK, LAX, or O'Hare, this limit may even be increased to 60 minutes. This rule is designed to ensure "on-time performance," as a single late bag can delay the entire loading process. If you miss this window, you may be forced to rebook on a later flight or, if the agent is feeling generous, your bag might be "gate-checked" (if it fits through security) or sent on the next available flight, though the latter often carries a risk of your luggage not arriving when you do.