The FAA issued an airworthiness directive for the Piaggio Avanti baggage door based on an in-flight baggage door opening due to a defective locking mechanism or installation. The warning light went on properly before the event, but the pilot, who misinterpreted it as a false warning, ignored it. The AD describes the unsafe condition as the baggage door lock pins not engaging properly, which can result in the baggage door open light illuminating when the baggage door is not open, leading to pilots’ disregarding a valid warning.