The US Army helicopter involved in Wednesday's midair collision with American Airlines flight 5342 had been practicing for the event of an attack on the capital. Officials have confirmed that the three soldiers, who all perished, had been rehearsing a plan that involves the evacuation of the White House when their Black Hawk collided with the passenger jet just before 9pm on Wednesday night. Defense sources confirmed the nature of the training exercise to CBS News, after internet sleuths had floated a theory online that it was doing exactly what sources say. Theorists had flooded social media with claims that...