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.