Narrative:

Taxiing on taxiway K for takeoff on runway 4L at the bos airport. The first officer was giving a departure briefing to the passenger and I, as the PIC, was working the radios. After switching from ground to tower the tower called us and I answered that we were ready for takeoff. The tower controller then cleared us for takeoff on runway 4L, and I replied that we were clear to go on runway 4L. We accomplished the line-up checklist and performed a normal takeoff on runway 4L. After takeoff, on the climb out through 300 ft MSL, the tower controller cleared us for takeoff again with instructions to turn left to 010 degrees and to contact departure. The first officer informed him that we were already airborne, the controller hesitated, and then switched us over to departure. Nothing further was said. The conditions at the airport on this morning were low IFR (1 1/2 mi visibility, 3 overcast, rain and fog). I don't know whether these conditions hindered the controller's ability to visually confirm our takeoff, or whether or not he forgot that he had already cleared us for takeoff. I do know that I had a very unpleasant feeling on that climb out wondering where the communication had broken down. I know for a fact that I read back cleared for takeoff on runway 4L, and my first officer had heard it as well.

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Original NASA ASRS Text

Title: FLC RECEIVES CLRNC FOR TKOF AFTER HAVING TAKEN OFF IN RESPONSE TO A PERCEIVED PREVIOUS TKOF CLRNC.

Narrative: TAXIING ON TXWY K FOR TKOF ON RWY 4L AT THE BOS ARPT. THE FO WAS GIVING A DEP BRIEFING TO THE PAX AND I, AS THE PIC, WAS WORKING THE RADIOS. AFTER SWITCHING FROM GND TO TWR THE TWR CALLED US AND I ANSWERED THAT WE WERE READY FOR TKOF. THE TWR CTLR THEN CLRED US FOR TKOF ON RWY 4L, AND I REPLIED THAT WE WERE CLR TO GO ON RWY 4L. WE ACCOMPLISHED THE LINE-UP CHKLIST AND PERFORMED A NORMAL TKOF ON RWY 4L. AFTER TKOF, ON THE CLBOUT THROUGH 300 FT MSL, THE TWR CTLR CLRED US FOR TKOF AGAIN WITH INSTRUCTIONS TO TURN L TO 010 DEGS AND TO CONTACT DEP. THE FO INFORMED HIM THAT WE WERE ALREADY AIRBORNE, THE CTLR HESITATED, AND THEN SWITCHED US OVER TO DEP. NOTHING FURTHER WAS SAID. THE CONDITIONS AT THE ARPT ON THIS MORNING WERE LOW IFR (1 1/2 MI VISIBILITY, 3 OVCST, RAIN AND FOG). I DON'T KNOW WHETHER THESE CONDITIONS HINDERED THE CTLR'S ABILITY TO VISUALLY CONFIRM OUR TKOF, OR WHETHER OR NOT HE FORGOT THAT HE HAD ALREADY CLRED US FOR TKOF. I DO KNOW THAT I HAD A VERY UNPLEASANT FEELING ON THAT CLBOUT WONDERING WHERE THE COM HAD BROKEN DOWN. I KNOW FOR A FACT THAT I READ BACK CLRED FOR TKOF ON RWY 4L, AND MY FO HAD HEARD IT AS WELL.

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.