One described it as “some kind of plague” and another claimed sickly passengers had “greatly dilated pupils”. Fearing mass poisoning on board, the pilot decided to make an emergency landing in the southern Russian city of Volgograd. Doctors and paramedics from five ambulances rushed on board the Airbus A321-211, videos show. Several passengers were taken for urgent medical treatment. Their conditions were not immediately known. Particularly affected were passengers between rows 21 and 26 in economy class. A woman passenger from Sochi said left the aircraft in Volgograd: "I was woken by a young woman screaming for assistance. “She yelled...