(Reuters) – Russia has accused Ukraine of shooting down a military transport plane carrying 65 captured Ukrainian soldiers to a prisoner exchange. Ukraine has neither confirmed nor denied the accusation but has challenged details of Russia’s account and has demanded an international investigation. Here’s a summary of what we know so far. WHAT WAS THE PLANE AND WHO WAS ON BOARD? The aircraft was an Ilyushin Il-76, a large military transport plane designed to carry troops, cargo or weapons. Russia said that beside the 65 Ukrainian PoWs there were six Russian crew members and three Russian soldie…