B727 CREW TAXIING TO RWY AT ORD IS INSTRUCTED TO FOLLOW A CL65 THAT WAS GOING TO A DIFFERENT RWY.

Narrative

ORIGINAL TAXI CLRNC TO RWY 32L AT T10 FOLLOWING A REGIONAL JET. TAXI INSTRUCTIONS CHANGED AFTER INITIAL TURN TO TAXI TO RWY 4L VIA A; A6 ;J ;W; CREW WAS BUSY DOING CHKLIST; SO BUSY READING AND DOING CHKLIST; FO BUSY VERIFYING CHKLIST; CAPT BUSY TAXIING AND DOING CHKLIST. MISSED TURN AT TXWY 'W' AND PROCEEDED TO RWY 9L. TWR CLRED US INTO POS AND HOLD RWY 4L PRIOR TO US MAKING TURN AT W AND WE JUST CROSSED THE HOLD LINE FOR RWY 9L WHEN WE REALIZED WE WERE ON RWY 9L INSTEAD OF RWY 4L. NO PLANES WENT AROUND AND TOWER THEN CLRED US FOR TKOF FROM RWY 9L. NO INCURSIONS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR SAID IT WAS VERY BUSY AT THE TIME. HE SAID THE GND CTLR WAS ISSUING TAXI INSTRUCTIONS TO 5 OR 6 ACFT AT A TIME WITH LITTLE OR NO RESPONSE FROM PLTS. HE ALSO SAID THEIR TAXI INSTRUCTIONS INCLUDED A STATEMENT TO CONTACT TWR. HE STATED THE TURN ONTO TXWY W FOR RWY 04L MAY HAVE BEEN MISSED BECAUSE THEY HAD BEEN TOLD TO FOLLOW A CL65 GOING TO RWY 09L AND THE CREW WAS BUSY STARTING THE THIRD ENGINE AND DOING THE CHKLIST. HE SAID THE CAPTAIN; FOLLOWING AN INSTRUCTION TO GO INTO POS AND HOLD ON RWY 04L; REALIZED HIS MISTAKE ABOUT 10 FT PAST THE RWY 09L HOLD LINES.