Let me start off by saying our flight was only a 20 minute flight from Phoenix to Tucson on a US Airways flight.  Doesn't sound as bad as doing a 2 hour drive.  Our flight was supposed to leave Phoenix at 136 pm.  Approximately 20 minutes before we were supposed to leave- when we were supposed to be boarding- is when the flight crew began  doing the checks- keep in mind this plane had just come from Tucson- the boarding agent came over the intercome and stated that there was something wrong with the plane, while they did not know what exactly is wrong with it maintenance was working on it. ...