PIC OF B757 HAS TO ABORT HIS TKOF WHEN FO SLIDING WINDOW POPS OPEN AT 80 KTS. TKOF ABORTED. HAD RESPONDED AND REACTED TO CHKLIST CALL ON PREFLT. TKOF DELAYED FOR BRAKE AND TIRE CONSIDERATIONS.

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NORMAL CHKLISTS (BEFORE START; START; TAXI; AND TKOF) ACCOMPLISHED. TWICE REF IS MADE TO THE WINDOWS -- THE RESPONSE BEING CLOSED AND LOCKED. ON BOTH RESPONSES; I VISUALLY CHKED THE FORWARD LATCH AND THE CLOSED SIGN AND ALSO CHKED TO SEE IF THE LATCH WAS PHYSICALLY CLOSED. THE RESISTANCE SEEMED POSITIVE AND THE LATCH LOOKED PROPERLY SEATED. AS THE TKOF ROLL BEGAN; AT 80 KIAS THE WINDOW CRACKED OPEN AND FORWARD AIR PRESSURE BEGAN TO OPEN THE WINDOW. THE TKOF WAS ABORTED AT 90 KIAS AND ACFT BROUGHT COMPLETELY TO A SAFE STOP. ALL AFTER ABORT PROCS WERE FOLLOWED PER THE COMPANY MANUAL. UPON INSPECTION OF THE WINDOW; IT WAS DISCOVERED THAT THE LATCH HAD NOT COMPLETELY SECURED DUE TO THE WINDOWS OVER CTR LOCK HAD BEEN TURNED TO THE OPEN POS. HOWEVER; THE INDICATION OF THE CLOSE-OPEN SIGN HAD SHOWN CLOSED AND THE LATCH WHEN VIEWED FROM THE ANGLE LINE OF SIGHT LOOKED LOCKED AND; WITH HAND PRESSURE; IT FELT LOCKED. BOTH THE CAPT AND COPLT VIEWED THE REQUIRED ITEMS PRIOR TO TKOF AS HAVING BEEN IN THE PROPER LOCATION. SUPPLEMENTAL INFO FROM ACN 403136: BRAKE TEMP REACHED 300 DEGS. WAITED 5 MINS PER BRAKE COOLING CHART.