I would agree - Unless this portion of tape (with UBL) was a prearranged signal (qued code).....and allows for a fail safe (already known que by overseas AQ elements) regardless of if something should have happened to UBL while AQ operatives were in their final staging phases.
The next 7 to 21 days American's should be very observant and have a heighten SA of their surroundings....
Agree 100%.