China's flight of a suspected surveillance balloon over the United States appears to mark a more aggressive - albeit puzzling - espionage tactic than relying on satellites and the theft of industrial and defense secrets, security experts said.
Both the United States and China have for decades used surveillance satellites to keep an eye on each other from the air. But China's recent balloons - a White House official said this week's episode was not the first - have some in Washington scratching their heads.
