Kesselring's air fleet carried the burden of operations over Dunkirk, but Sperrle's men were also attacking shipping. Keller was ordered to destroy Belgian ports in support of the 18th Army, while 30 aircraft from Loerzer's II. "Fliegerkorps"—including 12 from KG 3—were lost in battle with Air Vice Marshal Keith Park's No. 11 Group RAF. Approximately 320 tons of bombs were dropped, which killed 21 German airmen prisoners of war awaiting transport to England and injured 100 more. From 27 May, Sperrle's I and II air corps attempted to gain air superiority over the Calais–Dunkirk area—Calais had fallen the previous day. Massow's "Jafü" 3 provided fighter escort. Over the ports, the German air fleets sank or damaged 89 ships (126,518 grt) and eight destroyers with a further 21 damaged. Sperrle and Kesselring failed to prevent the Dunkirk evacuation, despite flying 1,997 fighter, 1,056 bomber and 826 "strike" operations.