Narrative:

At las vegas, I called ready for takeoff and blocked a tower radio transmission. Then I said 'blocked.' the tower controller cleared us into position and hold, which I repeated. We ran the below the line checklist, and after completion I said 'pre-takeoff checklist complete, cleared for takeoff.' the captain replied, 'cleared to go?' I said yes, and we took off. While rolling, the captain saw an aircraft crossing the runway well downfield. He called it out to me (I was at the controls) and asked me if I was sure we were cleared for takeoff. I thought back on our clearance, and said 'no, he said position and hold.' at this point the crossing aircraft was off our runway, and the captain told tower we were taking off (our speed was close to V1). Tower said that they only cleared us to position and hold, the captain said 'I realize that now, but we're committed.' the two airplanes never got close, and the rest of the flight was uneventful. No excuse, should have paid more attention, then asked for a retransmission when one of us was unsure.

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Original NASA ASRS Text

Title: A B737 FLC TOOK OFF WITHOUT A CLRNC AFTER THE FO (RPTR) CONFUSED THE POS AND HOLD CLRNC WITH A CLRNC FOR TKOF. THE CAPT QUESTIONED THE CLRNC WITHOUT AVAIL, AND THEN QUESTIONED AGAIN, DURING TKOF, WHEN ANOTHER ACFT CROSSED THE RWY DOWNFIELD. THE CAPT THEN INFORMED THE CTLR THAT THE FLC WAS TAKING OFF.

Narrative: AT LAS VEGAS, I CALLED READY FOR TKOF AND BLOCKED A TWR RADIO XMISSION. THEN I SAID 'BLOCKED.' THE TWR CTLR CLRED US INTO POS AND HOLD, WHICH I REPEATED. WE RAN THE BELOW THE LINE CHKLIST, AND AFTER COMPLETION I SAID 'PRE-TKOF CHKLIST COMPLETE, CLRED FOR TKOF.' THE CAPT REPLIED, 'CLRED TO GO?' I SAID YES, AND WE TOOK OFF. WHILE ROLLING, THE CAPT SAW AN ACFT XING THE RWY WELL DOWNFIELD. HE CALLED IT OUT TO ME (I WAS AT THE CTLS) AND ASKED ME IF I WAS SURE WE WERE CLRED FOR TKOF. I THOUGHT BACK ON OUR CLRNC, AND SAID 'NO, HE SAID POS AND HOLD.' AT THIS POINT THE XING ACFT WAS OFF OUR RWY, AND THE CAPT TOLD TWR WE WERE TAKING OFF (OUR SPD WAS CLOSE TO V1). TWR SAID THAT THEY ONLY CLRED US TO POS AND HOLD, THE CAPT SAID 'I REALIZE THAT NOW, BUT WE'RE COMMITTED.' THE TWO AIRPLANES NEVER GOT CLOSE, AND THE REST OF THE FLT WAS UNEVENTFUL. NO EXCUSE, SHOULD HAVE PAID MORE ATTN, THEN ASKED FOR A RETRANSMISSION WHEN ONE OF US WAS UNSURE.

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.