By the time I./JG 21 was ordered to the coastal area of the English Channel the "Gruppe" was redesignated III./"Jagdgeschwader" 54 (JG 54). Ostermann's third aerial victory on 12 August 1940 may have been over Flight Lieutenant E.B.B. Smith of No. 610 Squadron RAF, who bailed out of his Supermarine Spitfire I "K9818". Smith was rescued from the Channel and hospitalized. On 8 October 1940 Ostermann claimed his 7th aerial victory of the war and 5th of the Battle of Britain. His opponent may have been the Czech Sergeant Josef František who was killed flying Hurricane Mk. I "R4175" from No. 303 Polish Fighter Squadron near Sutton, west of Croydon, in the southern outskirts of London that day. The reason for his fatal crash remains unclear. Apart from Ostermann's claim, "Leutnant" (Second Lieutenant) Max Clerico and "Feldwebel" (Sergeant) Fritz Oeltjens also claimed one aircraft each at the same time and in the same vicinity. On 5 September 1940, III./JG 54's "Gruppenkommandeur" (group commander) failed to return from a mission and "Geschwaderkommodore" Hannes Trautloft temporarily appointed "Oberleutnant" Günther Scholz to lead the "Gruppe". The leadership of 7. "Staffel" (7th squadron) was filled by "Oberleutnant" Hans-Ekkehard Bob, who became one of Ostermann's mentors. During an escort mission on 30 September 1940, Bob and Ostermann claimed one Spitfire shot down each. In return Ostermann's wingman was shot down and made a forced landing at Bexhill. He radioed his fellow pilots: ""Spinat vier meldet sich ab nach Kanada"—Spinach 4 reports off for Canada".