By March 1939, 21 flying squadrons had been formed, the 20 surviving units being 'embodied' (included) with the Royal Air Force at the outbreak of war. Notably, all enlisted men continued to serve under their auxiliary conditions of service until they expired when they were required to transfer to the RAFVR. The squadrons were equipped with a variety of operational aircraft which included Hurricanes and Spitfires. The squadrons scored a number of notable successes before and during the Second World War: the first flight over Mount Everest, undertaken by auxiliary pilots from 602 Squadron, the first German aircraft destroyed over British territorial waters – and over the mainland, the first U-boat to be destroyed with the aid of airborne radar, the first kill of a V-1 flying bomb; the first to be equipped with jet-powered aircraft, and the highest score of any British night fighter squadron. In the Battle of Britain, the AAF provided 14 of the 62 Squadrons in RAF Fighter Command's Order of Battle and accounted for approximately 30% of the accredited enemy kills. Indeed, in 11 Group Fighter Command, that saw the heaviest fighting over South East England in 1940, of the 15 top scoring squadrons, eight were auxiliary. The losses sustained during the Battle of Britain, as with all other squadrons, were replaced by drafting in regular and RAFVR pilots. In fact, the volunteer reserves of the RAF outnumbered the regular RAF pilots in the Battle of Britain.