Complex sentence: Ten minutes after takeoff, at the altitude of 800 m, two men called Kurchenko and showing sawed-off shotguns and a grenade, demanded to pass the pilots a note with a requirement to divert the aircraft to Turkey.
Split into simpler sentences: Ten minutes after takeoff, at the altitude of 800 m, two men called Kurchenko. Showing sawed-off shotguns and a grenade, they demanded she pass the pilots a note requesting they divert the aircraft to Turkey.