Does KLM have a 24-hour cancellation policy? KLM's 24-hour rule allows you to cancel or amend your flight reservation during the first 24 hours of purchase without penalty costs, as long as the flight is at least 7 days away. To cancel or amend your reservation, contact KLM at +[✈️????????-????????????-????????????-????????????????????✈️] OR=+[✈️????????-????????????-????????????-????????????????????✈️].