Narrative:

Climbing out of dca we were using a flight # of 17. The controller called flight XY16 and gave a climb to 17000'. We knew that there was no XY16,but waited to see if anyone would answer. The controller had also asked XY16 to fly heading 300 degrees and intercept J518. The controller seemed nervous and needed a reply, plus the routing he had given was normal for our flight. We figured he had meant to call us with this clearance. We asked him if he had meant the last transmission for XY17. He replied yes and repeated the last part of the instructions 'heading 300, intercept J518.' we complied with all of his last transmission, including the climb to 17000'. Later the controller called back to tell us to descend back to 16000'. Because of a traffic conflict (3 mi to our left). He told us that he had only cleared us to 16000', but we both heard him say 17000' and set it immediately in the altitude alerter. Thinking back on it all, we figure he got mixed up on the call sign and the altitude. Our correct call sign was XY17, but he called us XY16 and cleared us to 17000', when he should have said XY17 cleared to 16000'. We should have gotten a complete readback on the clearance back when we first asked him if he was talking to us.

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Original NASA ASRS Text

Title: A MIX-UP OF FLT #'S BY CTLR AND INTERP BY FLT CREW RESULTS IN AN ALT EXCURSION AND A POTENTIAL CONFLICT. CTLR BECAME AWARE OF SITUATION AND AMENDED CLRNC TO DESCEND TO ORIGINAL ALT.

Narrative: CLBING OUT OF DCA WE WERE USING A FLT # OF 17. THE CTLR CALLED FLT XY16 AND GAVE A CLB TO 17000'. WE KNEW THAT THERE WAS NO XY16,BUT WAITED TO SEE IF ANYONE WOULD ANSWER. THE CTLR HAD ALSO ASKED XY16 TO FLY HDG 300 DEGS AND INTERCEPT J518. THE CTLR SEEMED NERVOUS AND NEEDED A REPLY, PLUS THE ROUTING HE HAD GIVEN WAS NORMAL FOR OUR FLT. WE FIGURED HE HAD MEANT TO CALL US WITH THIS CLRNC. WE ASKED HIM IF HE HAD MEANT THE LAST XMISSION FOR XY17. HE REPLIED YES AND REPEATED THE LAST PART OF THE INSTRUCTIONS 'HDG 300, INTERCEPT J518.' WE COMPLIED WITH ALL OF HIS LAST XMISSION, INCLUDING THE CLB TO 17000'. LATER THE CTLR CALLED BACK TO TELL US TO DSND BACK TO 16000'. BECAUSE OF A TFC CONFLICT (3 MI TO OUR LEFT). HE TOLD US THAT HE HAD ONLY CLRED US TO 16000', BUT WE BOTH HEARD HIM SAY 17000' AND SET IT IMMEDIATELY IN THE ALT ALERTER. THINKING BACK ON IT ALL, WE FIGURE HE GOT MIXED UP ON THE CALL SIGN AND THE ALT. OUR CORRECT CALL SIGN WAS XY17, BUT HE CALLED US XY16 AND CLRED US TO 17000', WHEN HE SHOULD HAVE SAID XY17 CLRED TO 16000'. WE SHOULD HAVE GOTTEN A COMPLETE READBACK ON THE CLRNC BACK WHEN WE FIRST ASKED HIM IF HE WAS TALKING TO US.

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.