If you've ever observed a boarding gate from afar, slept on a flight or excessively fidgeted, the Transportation Security Administration may have taken notes. Under its "Quiet Skies" program -- exposed by the Boston Globe on Saturday -- undercover air marshals have been surveilling some domestic air travelers who are not on a terrorist watch list or suspected of wrongdoing. The TSA says the program helps it thwart terrorists, but civil liberties advocates say it's an illegal invasion of privacy. We'll take up the issues.