South Korea moves to upgrade Black Hawk helicopters / Black Hawk helicopter may not have heard order to go behind American Airlines jet / DC plane crash: Black Hawk helicopter was on a 'continuity of government' drill / Mapped: How American Airlines plane collided with Black Hawk army helicopter near Washington DC airport / Third soldier inside Black Hawk helicopter involved in DC midair collision identified / Experts ask why Black Hawk chopper may have been flying above allowed altitude / Black Hawk chopper involved in D.C. collision was on training flight / What's it's like flying in a Black Hawk helicopter