Nachtjagdgeschwader 1 (NJG 1—1st Night Fighter Wing). His former unit, I./ZG 1 formed the nucleus of I. Gruppe of NJG 1 which was placed under the command of Oberleutnant (First Lieutenant) Werner Streib. Now flying in the 3. Staffel of NJG 1, Gildner claimed his first aerial victory as a night fighter pilot on the night of 2/3 September 1940. The bomber, a Handley Page Hampden from the RAF No. 144 Squadron, was shot down near Sittard on its mission to bomb Ludwigshafen. The Hampden was identified as P4370, the pilot and another crewmember were taken prisoner of war and two further crewmembers were killed in action. On 18/19 September 1940, Gildner was credited with the destruction of two Armstrong Whitworth Whitley bombers. The first bomber was Whitley V P5008 from No. 58 Squadron was on a bombing mission to Hamm and crashed southeast of Groenlo. The second Whitley N1425 from No. 77 Squadron, on a mission to Soest, was shot down near Zieuwent. On 13 March 1941 Gildner accounted for Wellington Mark I C N2746 BU-M from 214 Squadron during a British attack on Hamburg. Flight Lieutenant Dickinson, DFC, and his crew with the exception of the tail gunner, perished. Gildner was photographed inspecting the wreck. Gildner achieved another success on 8 April, downing Sergeant Boyer's No. 51 Squadron RAF Whitley T4298 near Gröningen. Five of the crew including Boyer became prisoners. On 9 July 1941, after his 16th aerial victory, 14 of which claimed at night, Gildner was awarded the Knight's Cross of the Iron Cross (). Following Falck and Streib, he was the third soldier of the night fighter force and first noncommissioned officer to receive this distinction. The presentation of the Knight's Cross was made by Kammhuber, at the time commander of the 1. Nachtjagd-Division (1st Night Fighter Division). Whitley V Z9306 KN-S, No. 77 Squadron RAF, formed part of the Düsseldorf raid during the night of 27/28 December 1941. Gildner shot it down over Friesland northwest of Leeuwarden near 'Zwarte Haan'. Four of the crew died from exposure after landing in the water. Their names, ranks and family are memorialised in the cemetery at the town Sint Jacobiparochie. With 21 nocturnal aerial victories claimed, Gildner was the second highest scoring night fighter pilot at the end of 1941. At the time, in first place was Streib with 22 nocturnal aerial victories claimed, and in third