Originally Posted by
Often1
Here is a list of the forms of ID accepted by TSA. Even if you don't have any of those, there may still be a way through the checkpoint. Unless you are checking luggage, you may never need to show any ID to WN or any carrier for a domestic flight.
http://www.tsa.gov/travel/security-s...identification
Note that the list at the link says "U.S. passport." It does
not say "valid U.S. passport" or "unexpired U.S. passport." The people who write these rules are very careful about precise phrasing. If they meant that it had to be unexpired, they would have said so. An expired passport is not valid for international travel, but in at least one situation I'm familiar with it was accepted for identification. (It was recent enough that the photo still looked like the bearer.)
So, your expired passport - which is still a U.S. passport by any definition - is probably still fine for this purpose.