Narrative:

Flight was cleared from gate to runway 22L via 'right turn on the inner, runway 9R parallel, runway 14L parallel, inner bridge, inner more to follow.' approaching the wedge from the north on the inner, we queried ground control for further instructions and were cleared 'left turn at the wedge, cargo, left through the hardstands to runway 22L.' after we turned on the cargo, we were cleared to tower frequency. While still on the cargo and 5 mins taxi time from runway 22L, we were cleared for takeoff. The clearance was read back by the first officer. We remarked at the time to each other that it was kind of early for takeoff clearance, but as tower didn't seem busy and we had both heard the clearance, we didn't question it further. After we were airborne, tower asked us where we were. We told them and, after giving us a couple of vectors on course, tower had us change to departure. When we checked in with departure, we were directed to check our transponder code. We did and found that the right hand numeral had slipped one digit. We attributed the previous flurry of radio calls to the slipped transponder code. 2 legs later, on the morning of aug/xx/93, just after getting airborne for sioux falls (fsd) we were told to contact ord tower after we arrived at fsd. When we did so, we were informed by the 'area supervisor' that the tapes showed that we took off without clearance but that no action was contemplated by ATC. I still think that we had takeoff clearance, but I'll certainly question early clrncs in the future.

Related reports:

Google
 

Original NASA ASRS Text

Title: FLC OF AN MLG ACR ACFT INADVERTENTLY TOOK OFF WITHOUT CLRNC.

Narrative: FLT WAS CLRED FROM GATE TO RWY 22L VIA 'R TURN ON THE INNER, RWY 9R PARALLEL, RWY 14L PARALLEL, INNER BRIDGE, INNER MORE TO FOLLOW.' APCHING THE WEDGE FROM THE N ON THE INNER, WE QUERIED GND CTL FOR FURTHER INSTRUCTIONS AND WERE CLRED 'L TURN AT THE WEDGE, CARGO, L THROUGH THE HARDSTANDS TO RWY 22L.' AFTER WE TURNED ON THE CARGO, WE WERE CLRED TO TWR FREQ. WHILE STILL ON THE CARGO AND 5 MINS TAXI TIME FROM RWY 22L, WE WERE CLRED FOR TKOF. THE CLRNC WAS READ BACK BY THE FO. WE REMARKED AT THE TIME TO EACH OTHER THAT IT WAS KIND OF EARLY FOR TKOF CLRNC, BUT AS TWR DIDN'T SEEM BUSY AND WE HAD BOTH HEARD THE CLRNC, WE DIDN'T QUESTION IT FURTHER. AFTER WE WERE AIRBORNE, TWR ASKED US WHERE WE WERE. WE TOLD THEM AND, AFTER GIVING US A COUPLE OF VECTORS ON COURSE, TWR HAD US CHANGE TO DEP. WHEN WE CHKED IN WITH DEP, WE WERE DIRECTED TO CHK OUR XPONDER CODE. WE DID AND FOUND THAT THE R HAND NUMERAL HAD SLIPPED ONE DIGIT. WE ATTRIBUTED THE PREVIOUS FLURRY OF RADIO CALLS TO THE SLIPPED XPONDER CODE. 2 LEGS LATER, ON THE MORNING OF AUG/XX/93, JUST AFTER GETTING AIRBORNE FOR SIOUX FALLS (FSD) WE WERE TOLD TO CONTACT ORD TWR AFTER WE ARRIVED AT FSD. WHEN WE DID SO, WE WERE INFORMED BY THE 'AREA SUPVR' THAT THE TAPES SHOWED THAT WE TOOK OFF WITHOUT CLRNC BUT THAT NO ACTION WAS CONTEMPLATED BY ATC. I STILL THINK THAT WE HAD TKOF CLRNC, BUT I'LL CERTAINLY QUESTION EARLY CLRNCS IN THE FUTURE.

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.