sentences:  Late in World War II, RAF and USAAF bombers that had been damaged in raids over the Reich would put down in Soviet-controlled territory rather than try to make it back to Western bases, and in April 1945 the Soviet Air Force issued a directive to its units in the field to report the location of any aircraft of its Western Allies that were in Soviet hands; among the aircraft salvaged were a total of 73 B-17s.The Fortresses that were in the best condition were returned to the USAAF, but a number were retained as interim heavy bombers.Although Russian aircrews and maintenance crews had no experience with such aircraft, the Soviets proved ingenious at keeping them flying, and in fact were delighted with the B-17's handling, comparing it to a "swallow" and the nimble Po-2 biplane trainer.