attacked by Bf 109s and Bf 110s over Bouzonville, a Bf 109 being shot down at Apach and a Bf 110 north-west of Bitche; a Hurricane pilot was killed trying to land at Brienne-le-Château. April – 9 May Most incursions in April were the usual reconnaissance flights but larger formations of fighters patrolled the front line and formations of up to three squadrons () flew at high altitude as far as Nancy and Metz. Reconnaissance aircraft began to cross the front line in squadron strength to benefit from greater firepower on the most dangerous part of the journey, before dispersing towards their objectives. Hurricanes shot down a Bf 109 on 7 April at Ham-sous-Varsberg and on 9 April, when the Germans began the invasion of Denmark and Norway (Operation Weserübung), Bomber Command aircraft were diverted to operations in Scandinavia and the Battle squadrons took over leaflet raids over Germany by night; no aircraft were lost. The situation was unchanged until the night of 9/10 May, when the heavy artilleries of the German and French armies began reciprocally to bombard the Maginot and Siegfried lines. In early May, the AASF had bombers, serviceable bombers being Battles. The had fewer than a hundred bombers, cent of which were obsolescent. The in the west had aircraft, including about and bombers. Battle of France () 10 May As dawn broke, German bombers made a coordinated, hour-long attack on 72 airfields in the Netherlands, Belgium and France, inflicting severe losses on the Belgian Air Component (/) and the Royal Netherlands Air Force (). The bombers flew in formations of three to thirty or but had least effect on the British and French airfields, over which British and French fighters intercepted the German raiders. Nine British-occupied bases were attacked to little effect. Hurricanes of 1 Squadron at Vassincourt patrolled the Maginot Line from and shot down a for one Hurricane damaged. At A Flight shot down a Do 17 near Dun-sur-Meuse for one Hurricane crash-landed. At Rouvres, two 73 Squadron Hurricanes attacked three bombers over the airfield, damaging one for a Hurricane forced down damaged. At four Hurricanes attacked eleven Do 17s near the airfield, one Hurricane landing in flames with a badly burned pilot and one Hurricane returning damaged. More Hurricanes were scrambled and shot down two Do 17s; a He 111 was shot down soon afterwards. Orders to 73 Squadron led to it moving