Large transport began takeoff without clearance and was told to abort.

Attributes
ACN	90528
Time
Date	198807
Day	Fri
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : ord
State Reference	IL
Altitude	agl bound lower : 0 agl bound upper : 0
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	climbout : takeoff other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 240 flight time total : 14000 flight time type : 1500
ASRS Report	90528
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	non adherence : clearance other anomaly other
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Holding in position on runway 32L (full length) other aircraft taking off at runway 32L, T1. Tower informed us we were going to takeoff before a widebody transport. 2 large transport's took off and widebody transport was holding short at T1. Our call sign air carrier xyx. (They were also landing on runway 27L.) tower said (we thought), 'air carrier xyx, cleared for immediate takeoff.' we read back, 'air carrier xyx, cleared for takeoff.' we turned on all landing lights, added takeoff power and started takeoff roll. Tower called, 'air carrier xyx, stop takeoff now,' and we did (at speed less than 60 KTS). The widebody transport was air carrier yx and although not on the runway, was cleared for 'immediate' takeoff. The cause was similar call signs, we were in position and primed for takeoff, and the use of word 'immediate' to aircraft not on runway.

Original NASA ASRS Text

Title: LGT BEGAN TKOF WITHOUT CLRNC AND WAS TOLD TO ABORT.

Narrative: HOLDING IN POS ON RWY 32L (FULL LENGTH) OTHER ACFT TAKING OFF AT RWY 32L, T1. TWR INFORMED US WE WERE GOING TO TKOF BEFORE A WDB. 2 LGT'S TOOK OFF AND WDB WAS HOLDING SHORT AT T1. OUR CALL SIGN ACR XYX. (THEY WERE ALSO LNDG ON RWY 27L.) TWR SAID (WE THOUGHT), 'ACR XYX, CLRED FOR IMMEDIATE TKOF.' WE READ BACK, 'ACR XYX, CLRED FOR TKOF.' WE TURNED ON ALL LNDG LIGHTS, ADDED TKOF PWR AND STARTED TKOF ROLL. TWR CALLED, 'ACR XYX, STOP TKOF NOW,' AND WE DID (AT SPD LESS THAN 60 KTS). THE WDB WAS ACR YX AND ALTHOUGH NOT ON THE RWY, WAS CLRED FOR 'IMMEDIATE' TKOF. THE CAUSE WAS SIMILAR CALL SIGNS, WE WERE IN POS AND PRIMED FOR TKOF, AND THE USE OF WORD 'IMMEDIATE' TO ACFT NOT ON RWY.

Data retrieved from NASA's ASRS site as of August 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.