Washington airspace alert sparks White House lockdown

The White House and US Congress were locked down for nearly an hour Tuesday over a suspected airspace intrusion over Washington, but hours later officials still had no explanation for what triggered the alert.Major Andrew Hennessy, a spokesman for the North American Aerospace Defense Command, told AFP that "a track of interest" appeared on radars early Tuesday, sparking concern.A US Coast Guard helicopter deployed by NORAD to investigate what appeared to be an unidentified aircraft nearing tight