On 27 May 1940, in one of the final mass encounters of the "Blitzkrieg", 13 Hurricanes from 501 Squadron intercepted 24 Heinkel He 111s escorted by 20 Bf 110s; during the ensuing battle, 11 Heinkels were claimed as "kills" and others damaged, with little damage to the Hurricanes. On 7 June 1940, "Cobber" Kain, the first RAF ace of the war, got word that he was to return to England for "rest leave" at an Operational Training Unit. On leaving his airfield, he put on an impromptu aerobatic display and was killed when his Hurricane crashed after completing a loop and attempting some low altitude "flick" rolls.