[3] This was a wing in name only, being just a single Gruppe (Fighter Group) that had been set up just prior to the outbreak of war, in July 1939.

On a mission over the English Channel, he claimed a Bristol Blenheim bomber shot down 10 kilometers (6.2 miles) east of Saint-Omer.

During a period of the battle of Britain referred to as Kanalkampf, Staiger claimed a Spitfire northwest of Cap Gris-Nez on 8 July, and a Blenheim 15 kilometers (9.3 miles) northeast of Deal on 11 July, and another Spitfire on 4 August in a location 10 kilometers (6.2 miles) southwest of Dover.

At Krefeld, the Gruppe received the then new Messerschmitt Bf 109 F-1, training on this type until they relocated to Saint-Omer, France on 14 February 1941.

[13] By 15 June, JG 51 had completed its preparation for Operation Barbarossa, the German invasion of the Soviet Union and was based at airfields at Siedlce, Stara Wieś, Halasy where III.

[14][15] The attack on the Soviet Union began at 03:45 on 22 June with JG 51 flying fighter patrols along the Bug River.

On 14 July, he was seriously injured when his Bf 109 F-2 (Werknummer 8083—factory number) was hit by Soviet anti-aircraft fire and shot down near Stara Bychow, approximately 50 kilometres (31 miles) south of Mogilev on the Dnieper.

[19][20] After an extended period of convalescence he served in a number of pilot-training units for the next two years, and was promoted to Hauptmann (Captain) on 1 February 1943.

Staiger briefly returned to JG 51 on the Eastern Front where he claimed a Lavochkin-Gorbunov-Gudkov LaGG-3 fighter shot down while flying with 9.

Staffel of Jagdgeschwader 26 "Schlageter" (JG 26—26th Fighter Wing), replacing Oberleutnant Erwin Leykauf who was transferred.

[25] The next day during Blitz Week, the USAAF attacked synthetic rubber factories in Hannover and U-boat shipbuilding facilities in Hamburg.

Staiger and Unteroffizier Hans Oeckel both claimed a B-17 shot down but both pilots were wounded by the defensive gun fire of the bombers.

[39] On 21 January, the USAAF Ninth Air Force attacked several V-1 flying bomb launch sites.

[41] On 20 February, the Eighth Army Air Force, formerly known as VIII Bomber Command, launched Operation Argument, also known as "Big Week", a series of attacks on the German aircraft industry.

[47] Two days later, the Eighth Army Air Force continued the attack on the German aircraft industry and Staiger claimed a B-17 bomber shot down over Colmar.

[49] Defending against an attack on southern Germany, Staiger claimed his 50th aerial victory when he shot down a Fifteenth Air Force B-17 bomber near Wiener Neustadt.

Gruppe on 24 April, Staiger claimed five aerial victories, potentially making him an ace-in-a-day when the Eighth Army Air Force attacked Luftwaffe targets at Munich, Oberpfaffenhofen and Friedrichshafen.

Staiger's Bf 109 was equipped with the MK 108 cannon, firing 30 mm (1.2 in) mine and high-explosive incendiary shells through the propeller hub.

[51][52][53] On 15 May 1944, Staiger was transferred and appointed Gruppenkommandeur (group commander) of the Focke-Wulf Fw 190-equipped I. Gruppe of JG 26, replacing Major Karl Borris.

[58] Three days later on 23 June, Staiger was credited with shooting down a Spitfire fighter west of Rouen, northeast of Bayeux.

[59] On 25 June, Staiger claimed another 370th Fighter Group P-38 near Rouen in combat over on the eastern area of the invasion front.

[64] On 10 August, during the German failed counter-attack named Operation Lüttich, Staiger claimed a Spitfire fighter shot down near Granville/Avranches.

[66] At Reinsehlen, the Gruppe was assigned new pilots, predominately directly coming from the Hitler Youth, no older than 18 to 20 years and lacking any combat experience.

Gruppe relocated to Tutow, approximately 40 kilometers (25 miles) north of Neubrandenburg, where Staiger continued to train his new pilots which was impacted by lack of fuel.

Gruppe moved to an airfield at Drope, located approximately 15 kilometers (9.3 miles) east-northeast of Lingen, on 17 December.

[70] On 24 December, the Eighth Army Air Force launched its largest attack of the war, sending more than 2,000 heavy bombers against numerous Luftwaffe airfields.

Gruppe of Ergänzungs-Jagdgeschwader 2 (EJG 2—2nd Supplementary Fighter Wing) for conversion training to the then new Messerschmitt Me 262 jet aircraft.

Nowotny, a fighter pilot credited with 258 aerial victories and recipient of the Knight's Cross of the Iron Cross with Oak Leaves, Swords and Diamonds (Ritterkreuz des Eisernen Kreuzes mit Eichenlaub, Schwertern und Brillanten), had been assessing the Me 262 under operational conditions.

[78] According to Spick, Staiger was credited with 63 aerial victories claimed in over 400 combat missions, including 26 heavy bombers.

[80] According to Weal, Staiger, together with Oberleutnant Hugo Frey, was the most successful fighter pilot against the heavy bombers while flying the Bf 109.