MOSCOW - A son of the president of Russia's oil-rich region of Tatarstan was named among a list of 50 people killed aboard a Boeing 737 plane that crashed in the region's capital on Sunday.Tatarstan President Rustam Minnikhanov's son, Irek, was on the flight from Moscow to Kazan, according to a passenger list posted news websites whose authenticity was confirmed by the regional government.The Tatarstan Airlines plane was trying to abort its landing in order to make a second approach, but it exploded on hitting the runway, killing all 44 passengers and six crew on board, emergency officials said.