UNAUTH TKOF -- ACR IS TOLD TO TAXI ONTO THE RWY AND BE PREPARED FOR AN IMMEDIATE TKOF AND THAT THERE WAS AN ACFT ON FINAL APCH. THE FLC ROLLED ONTO THE RWY AND THE CAPT SPOOLED UP THE ENGS AND SAID TO THE FO 'YOU GOT THE ACFT.'

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ON TAXI OUT TWR CHANGED RWY FOR TKOF FROM RWY 11R TO RWY 11L. CREW WAS CONDUCTING TAXI CHKLIST. SO STOPPED CHKLIST TO CHK RWY TKOF WT AND RECALCULATE REDUCED THRUST. AFTER THAT; THE TAXI CHKLIST WAS RESTARTED AND FINISHED AS WE APCHED THE RWY. FO SWITCHED TO TWR AS THE TWR CTLR WAS CALLING FLT TO GIVE IT CLRNC ON TO RWY. TWR CTLR SEEMED AGITATED THAT OUR FLT WAS NOT UP ON TWR SOONER AND CLRED US ONTO THE RWY. THE CREW READ BACK CLRNC AND COMPLETED BEFORE TKOF CHKLIST. CAPT TURNED OVER TO FO. BOTH SO AND FO ASKED CAPT IF FLT WAS CLRED FOR TKOF. CAPT SAID YES; AND FLT DEPARTED ARPT. ONCE FLT WAS SAFELY AIRBORNE; TWR INFORMED CREW THAT THEY WERE NOW CLRED FOR TKOF. THE CONVERSATION BTWN OUR FLT AND THE TWR AS WE CAME UP ON TWR FREQ IS WHAT LED TO THIS PROB. THE TWR CTLR ADDED HIS AGGRAVATION TO THE CLRNC WHICH CAUSED CAPT TO 'THINK' THAT THE TWR WANTED FLT TO TKOF AS QUICK AS POSSIBLE. BOTH FO AND SO WERE NOT SURE IF A TKOF CLRNC HAD BEEN RECEIVED; BUT CAPT SEEMED EXTRA SURE THAT WE HAD. FO WAS TRAINING INSTRUCTOR WHO HAD RETURNED TO LINE AFTER A NUMBER OF MONTHS IN TRAINING.