Börngen was born 7 February 1916 in Meuselwitz, at the time in the Kingdom of Saxony within German Empire.

[4] On 20 May 1942, Börngen officially replaced Hauptmann (captain) Ernst Düllberg as Staffelkapitän (squadron leader) of 5.

Düllberg had been wounded in action on 22 November 1941 and Börngen had already acted as intermittent Staffelführer for some weeks.

[7] During the attack, his Bf 109 G-6  (Werknummer 18 371) took a cabin hit from the defensive fire of the bomber, wounding him severely.

[9] In defense of this attack, I. Gruppe engaged a formation of Boeing B-17 Flying Fortress bombers shortly past 12:30 just east of Eschborn.

In this encounter, the Gruppenkommandeur (group commander) of I. Gruppe, Major Ludwig Franzisket was severely wounded.

[11] On 19 May 1944, the Eighth Air Force targeted Berlin and Braunschweig with 888 heavy bombers, protected by 964 escort fighters.

The German aerial defenses under the command Jagdfliegerführer Ostmark ordered I. Gruppe, led by Börngen and at the time based at Fels am Wagram, to take off at 11:43.

[11] Following the encounter, JG 27 claimed 17 aerial victories, including Herausschüsse (separation shots)—a severely damaged heavy bomber forced to separate from his combat box which was counted as an aerial victory.

At 13:15, Börngen had shot down a B-24 near Helmstedt and then at 13:20 engaged another bomber by ramming it with his Bf 109 G-6 (Werknummer 441 101—factory number), sustaining severe injuries.