Tuesday, April 25, 2006File:Tu 16019.jpg A senior Russian air force commander has claimed that new, upgraded Tu-160 bomber aircraft were unchallenged by US air defense systems when they penetrated a radar zone near the Canadian coast in US territory during an April training exercise, reports the Russian news agency RIA Novosti. Commander of Russia’s long-range strategic bombers, Lieutenant General Igor Khvorov said that the bombers successfully carried out four mock