- KLM’s 24-hour rule allows passengers to cancel or adjust their flight booking within 24 hours of purchase without paying cancellation fees, provided the flight is at least seven days from departure. This applies to all ticket classes, including non-refundable options, and adheres to U.S. Department of Transportation regulations. A full refund will be processed if canceled within this period. The rule does not apply to bookings made within a week of departure or through third-party travel agencies. It’s advisable to check with KLM for any additional details.