Narrative:

We were operating as a tail-end ferry flight (chs-31J) after a 41 hour, 5 day international operation. IFR clearance was received by the first officer just before reaching chs runway 3. Clearance was given by chs control tower to enter runway 3. I understood that takeoff clearance had been issued, therefore followed through with takeoff run and liftoff. At 30-50 ft AGL, the control tower stated that we did not have takeoff clearance, that we were cleared for 'position and hold' only. Simultaneous with the control tower verbal transmission, I observed a fighter jet which either had made low approach or takeoff on runway 15. His position was at my 1 O'clock orientation as we both passed approximately 50 ft AGL. No evasive action was required as our respective flight paths were not in conflict. It is possible that after just hearing 'cleared as filed' as part of the IFR clearance readback, this I mistook this as cleared for takeoff, and inadvertently made an illegal takeoff as was indicated by chs control tower. I was unaware of the fighter's presence and unable to hear his xmissions so I suspect he was utilizing UHF. A contributing factor and surprise to me is that the control tower allowed our full takeoff run if we were not actually cleared for takeoff. A full cockpit awareness and understanding of the clearance might have allowed us to avoid the above and/or challenge the clearance if in question.

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Original NASA ASRS Text

Title: LGT MAKES TKOF WHEN CLRED TO POS AND HOLD. CLOSE PROX WITH MIL FGT.

Narrative: WE WERE OPERATING AS A TAIL-END FERRY FLT (CHS-31J) AFTER A 41 HR, 5 DAY INTL OP. IFR CLRNC WAS RECEIVED BY THE FO JUST BEFORE REACHING CHS RWY 3. CLRNC WAS GIVEN BY CHS CTL TWR TO ENTER RWY 3. I UNDERSTOOD THAT TKOF CLRNC HAD BEEN ISSUED, THEREFORE FOLLOWED THROUGH WITH TKOF RUN AND LIFTOFF. AT 30-50 FT AGL, THE CTL TWR STATED THAT WE DID NOT HAVE TKOF CLRNC, THAT WE WERE CLRED FOR 'POS AND HOLD' ONLY. SIMULTANEOUS WITH THE CTL TWR VERBAL XMISSION, I OBSERVED A FIGHTER JET WHICH EITHER HAD MADE LOW APCH OR TKOF ON RWY 15. HIS POS WAS AT MY 1 O'CLOCK ORIENTATION AS WE BOTH PASSED APPROX 50 FT AGL. NO EVASIVE ACTION WAS REQUIRED AS OUR RESPECTIVE FLT PATHS WERE NOT IN CONFLICT. IT IS POSSIBLE THAT AFTER JUST HEARING 'CLRED AS FILED' AS PART OF THE IFR CLRNC READBACK, THIS I MISTOOK THIS AS CLRED FOR TKOF, AND INADVERTENTLY MADE AN ILLEGAL TKOF AS WAS INDICATED BY CHS CTL TWR. I WAS UNAWARE OF THE FIGHTER'S PRESENCE AND UNABLE TO HEAR HIS XMISSIONS SO I SUSPECT HE WAS UTILIZING UHF. A CONTRIBUTING FACTOR AND SURPRISE TO ME IS THAT THE CTL TWR ALLOWED OUR FULL TKOF RUN IF WE WERE NOT ACTUALLY CLRED FOR TKOF. A FULL COCKPIT AWARENESS AND UNDERSTANDING OF THE CLRNC MIGHT HAVE ALLOWED US TO AVOID THE ABOVE AND/OR CHALLENGE THE CLRNC IF IN QUESTION.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.