The Mechelen incident of 10 January 1940, also known as the Mechelen affair, took place in Belgium during the Phoney War in the first stages of World War II. A German aircraft with an officer on board carrying the plans for Fall Gelb, the German attack on the Low Countries, crash-landed in neutral Belgium near Vucht in the modern-day municipality of Maasmechelen (Mechelen-aan-de-Maas) within the Province of Limburg. This prompted an immediate crisis in the Low Countries and amidst the French and British authorities, whom the Belgians notified of their discovery; however, the crisis abated relatively quickly once the dates mentioned in the plans passed without incident. It has been argued that the incident led to a major change in the German attack plan, but this hypothesis has also been disputed.