Some Americans have been trailed and closely monitored by undercover air marshals as they traveled on U.S. flights, as part of a previously undisclosed Transportation Security Administration program called Quiet Skies. The existence of the program was first reported Saturday by the The Boston Globe, citing an internal TSA bulletin from March as well as anonymous sources within the department. The Globe says the program targets travelers who are not on terrorist watch lists and are not suspected of a crime. Some air marshals involved have expressed misgivings about the domestic surveillance program, questioning whether it's legal and whether it's...