Originally Posted by
JDiver
Wrong - they misinformed you, using the old "it's policy" (misused almost as much as "it's because of security.") I travel with a roll-aboard all the time, and have never (on AA - BA is another kettle of fish) had a problem with standing by, minor and major flight changes, etc. (Whereas if I had been traveling with checked luggage, I'd have had at least a spot of trouble.)
While it may be not be official policy, it certainly is the policy of a fair number of gate agents who get the final say. We had a thread on it not too long ago, but LGA in particular seems to be a big fan of the "if you're a standby passenger, we're checking your carry-on" policy, regardless of when they clear the list.