I think that's a pretty good sign that you're on to something, and that the feds have no Consititutional basis to tell the airlines anything.
However, since we're talking about folks -- your soci congresshumanoids, the airline CEOs, Norman Mineta, and yes, George W. Bush -- who are unfamiliar with, indifferent, or hostile to the Constitution, let me hazard a guess as to how this is playing out. After 911, the feds fed the airlines $15 B (can that be right, or have I lost my mind?!) worth of federal catnip, and so the airlines aren't about to bite the hand that feeds them. Which is the way Leviathan tends to work these days.
Constitootion? We don't need no steenkeen' Constitootion!