Bader's left leg was amputated below the knee, his right leg above, but he had sufficient control of prosthetic legs to be able to drive a manual car (adapted with the clutch operated by the right foot and accelerator/brake by the left, rather than the more usual reverse). The foot controls of the Hurricane and Spitfire were quite simple - two pedals that controlled the rudder, Bader being able to operate them with his prosthetics without adaptation. Some aircraft of the time featured toe braking - hydraulic brakes operated by pivoting the foot pedals, which Bader would have been unable to do, but the Hurricane and Spitfire had hand operated air brakes. In that system a hand lever activated the brakes, the rudder pedals then used for differential braking.

Bader himself describes the process in the "'Plane' Advice" section of this Douglas Bader Foundation page.

Douglas Bader was hardly the only legless  fighter pilot, either!

There was Fleet Air Arm pilot Colin Hodgkinson, who had the rather fitting nickname "Hoppy." In May 1939, before the war had even started, Hodgkinson got into a mid-air collision on a training sortie. One leg had to be amputated below the knee, the other above the knee. After re-learning to walk, he was allowed back in the air in December 1940 as an observer-gunner.

Inspired by Bader's example, Hoppy wanted to get back in the cockpit. He transferred to RAF Fighter Command in 1942. Like Bader, he flew Spitfires. Like Bader, he shot down Germans (two German fighters, to be exact). And like Bader, he was captured after crashing. Unlike Bader, who spent the rest of war cooling his heels in Colditz and harassing the Germans with home-made propaganda leaflets, Hoppy was sent home in 1944 for medical reasons. After the war, he flew the de Havilland Vampire into the 1950s and wrote his appropriately-titled memoir: Best Foot Forward.

Over in the Soviet Union, there was double amputee Alexey Maresyev. With four kills under his belt, Mareseyev was well on his was to becoming an ace when his Yak-1 was shot down in April 1942. Badly wounded, Mareseyev pulled himself out of the cockpit of his wrecked aircraft. For the next 18 days, Mareseyev would crawl through German-held territory towards friendly lines. He made it to safety, but his frostbitten and gangrenous legs had to be amputated below the knees.

Mareseyev got new legs in hospital and started down his long road to recovery. He learned to walk, then to waltz (to improve his motor skills), and finally to fly again. In 1943, he returned to flying in the La-5 (or La-5FN, sources differ). Thankfully, the La-5 had pneumatically-operated brakes operated with a brake lever on the control column - this made it easier for a pilot with prosthetics to fly.

Despite his disability he went on to become a Hero of the Soviet Union and a double ace, with 11 kills - three of those kills were scored on the same day. After the war, he had a film and book made about him and lived to the ripe old age of 84.

In November 1941, Zakhar Artyomovich Sorokin, made a taran ramming attack on a Bf 110 in his MiG-3. Amazingly, he survived, but had to spend a week walking back to base in -40 C weather on frosbitten feet. His frozen feet had to be replaced with prosthetics. Sorokin went on to shoot down nine more (other sources say 13 more) German planes after being equipped with prostheses and became a Hero of the Soviet Union.

Another pilot by the name of L. Byelousov had already been injured badly in a pre-war crash. There's a reference to an "L. Byelousov" commmanding an I-153 squadron of the 13th IAP based in the Baltic around June 1941. Perhaps it's the same pilot? Either way, a final crash in December 1941 aggravated these old wounds and caused them to become infected. He lost his legs, but went on to score seven kills and become a Hero of the Soviet Union in 1957.