Okay, so this might not be "really" about captured aircraft, but some of you might find this interesting.
In April 1945 one damaged B-17 bomber force-landed on Yugoslav airfield at Sombor in northern Serbia, which was the base of Yugoslav 11th fighter wing equipped with Yak-3 fighters. American crew abandoned their airplane and with help of partisans returned to their base in Italy. The airplane was identified as Boeing B-17G-50 DL (number 44-6422) from 483rd BG 15th AF USAAF. Yugoslav mechanics and ground crews repaired it to flying condition using parts from other damaged airplanes of the same type that were "lying around" on this an other airfields across Yugoslavia.
But soon order came from partisan command that this B-17 is to be handed over to Soviets. This was done and Soviet pilots flew the airplane to the unknown destination in the east.
This "Yugoslav" Flying Fortress was marked with partisan markings - red stars - but only on the both sides of the fuselage, making strange combination of partisan/Soviet/American markings. All other American national and tactical markings remained unchanged.
The further fate of this B-17 in Soviet hands remains unknown.
The pictures were taken from "AEROmagazin"