I've done some research and found out why Hartmann and his party were turned over to the Soviets. During the Allied conference at Yalta Stalin demanded that the UK and USA must turn over any captured Axis troops that fought on the Eastern Front. FDR and Churchill thought that this stipulation would only apply to Ukrainians, Cossacks, Latvians, Estonians, Croatians, Yugoslav Chetniks, etc, that had lived in areas that Yalta assigned to the USSR's designated sphere of influence. This was later expanded to include German military personnel.

The Third Reich formally surrendered to the Western Allies on 7 May 1945, and the next day to the USSR . Regardless, the front lines were fluid and many small Axis formations, accompanied by civilian refugees, fought through Soviet lines after 7 May. Many frontline US Army units allowed the Germans to surrender to them. There was one case in which American troops held their fire and allowed Germans to flee across a bridge over the Elbe while the Wehrmacht fought a rear guard action to hold the Red Army back. Stalin squawked about the Allies giving sanctuary to "hitlerite" forces so the USA and UK began a policy of turning people back from their zones of occupation, and repatriating POWs back to Soviet control. This policy ended after a month or so, largely due to the murder of many of the repatriated POWs, which was sometimes done as the Western Allied forces watched.

Hartmann was turned over to the Soviets because he made it to US lines after 7 May. Another example of postwar repatriations was the case of the 3rd Waffen SS, the Totenkopf Division. In the closing week of the war what was left of the 3rd SS broke out of an encirclement and fought through to US lines. On 17 June the US Army marched them back to Soviet lines, and no Totenkopf personnel were ever repatriated back to West Germany as Hartmann was in 1955. The Brits repatriated units of Don Cossacks back to Red Army custody, and Chetnik and Ustaschi units that surrendered in the Brit sector of occupied Austria were turned over to Tito's Partisans for "disposal".

edit. Training new pilots became problematic for Germany as they lost air superiority over the Reich. By March 1945 American fighters prowled the skies over Germany at will. There were cases in which a student pilot's first solo flight became his first (and last) combat mission.

Good point reference the repatriation of POWs. Stalin had the ultimate trump card; all the American and British POWs held in stalags in the eastern Germany. About twenty years ago a book titled Soldiers of Misfortune created a stir when it revealed that Stalin held back a significant number of American POWs that fell into Soviet hands during the final months of the war. Maybe Stalin was mad that we took custody of many of the German rocket scientists and Abwehr intelligence personnel as the war ended.

Yes it does, on page 259. The squadron engineering officer fabricated hand controls in Rudel's plane, and in late April the mechanics devised a leg extension so his stump could work the rudder controls.