VJT518 COMMENCED TAXI AT 2045LT FOR RWY-25L. UPON REACHING THE HOLDING POINT OF RWY-25L, THE FLIGHT CREW WAS INSTRUCTED TO CONTACT TWR. HOWEVER, THE AIRCRAFT DID NOT ESTABLISH CONTACT WITH TOWER. AT 2052LT, VJT518 ENTERED RWY-25L, COMMENCED THE TAKE-OFF ROLL, AND BECOME AIRBORNE WITHOUT OBTAINING ATC TAKE-OFF CLEARANCE. UPON OBSERVING THE UNAUTHORIZED TAKE-OFF, THE TOWER CONTROLLER INSTRUCTED THE AIRCRAFT TO CANCEL THE TAKE-OFF, HOWEVER, THE PILOT REPORTED THAT THE AIRCRAFT HAD ALREADY DEPARTED. EARLIER, AT 2048LT, UAE602 (B777) HAD LANDED ON RWY-25R AND WAS SUBSEQUENTLY CLEARED TO CROSS RWY-25L VIA TWY-D. UPON OBSERVING THE TAKE-OFF ROLL OF VJT518, UAE602 STOPPED SHORT OF RWY-25L ON ITS OWN INITIATIVE AND, AFTER THE DEPARTURE UAE602 RESUMED TAXI TO STAND.
