THE TRUCK HAD BEEN PARKED WITH IGNITION OFF FOR 4 HOURS IN THE PARKING LOT BEHIND MY OFFICE. I WAS INSIDE AND HEARD THE HORN BLOW. ABOUT A MINUTE LATER I SMELLED SOMETHING BURNING AND THOUGHT THE BUILDING WAS ON FIRE. I WAS IN PANIC STATE RUNNING ROOM TO ROOM TRYING TO FIND WHERE THE SMELL WAS COMING FROM. I THEN NOTICED SMOKE COMING IN THE AIR VENTS OF THE BUILDING (MY TRUCK WAS PARKED LESS THAN 3 FEET FROM THE AIR CONDITIONING CENTRAL UNIT). I WENT OUT THE BACK DOOR AND THE TRUCK WAS ENGULFED IN FLAMES. THIS ALL HAPPENED IN 10 MINUTES OR LESS. TWO EMPLOYEES PARKED NEXT TO MINE HAD JUST LEFT 15 MINUTES PRIOR TO ME FINDING THE TRUCK IN FLAMES AND HAD NOTICED NOTHING. THERE WAS A RECALL A CRUISE CONTROL SWITCH AND I HAD TAKEN IT TO THE DEALERSHIP TO HAVE MINE DISCONNECTED A FEW YEARS BACK. I HAVE NO IDEA WHAT STARTED THE FIRE BUT APPARENTLY IT IS QUITE COMMON IN FORD F-SERIES TRUCKS AROUND THE 2001 YEAR MODEL TO SPONTANEOUSLY CATCH FIRE EVEN IF THEY HAVE BEEN SITTING FOR A WHILE WITH THE IGNITION OFF.