Narrative:

The CRJ2 was level FL210 eastbound to the left of the H25B. The H25B and the CRJ2 were route separated. The H25B was climbing to FL210. At the paleo intersection the H25B made a 90 degree left turn into the CRJ2. I asked the H25B where he was going and he said kerno, an arrival fix to an airport he was not cleared to. I checked my flight data information and it showed that the H25B was filed over agard for lga. When I told the pilot this, he said that he was going to mmu over kerno. Much confusion followed. I then told the H25B to maintain FL200. He was climbing out of FL196. The H25B got to FL203 before going back down, underneath the CRJ2 at FL210. The H25B filed 2 flight plans -- 1 to mmu and 1 to lga. Clearance delivery cleared the H25B to mmu but gave the H25B the beacon code on the flight plan to lga. Therefore, the H25B was going to mmu while my data showed him going to lga.

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Original NASA ASRS Text

Title: ZDC CTLR EXPERIENCED NEAR LOSS OF SEPARATION WHEN ENRTE ACFT AT FL210 MADE UNEXPECTED TURN BECAUSE OF FLT PLAN MIX-UP.

Narrative: THE CRJ2 WAS LEVEL FL210 EBOUND TO THE L OF THE H25B. THE H25B AND THE CRJ2 WERE RTE SEPARATED. THE H25B WAS CLBING TO FL210. AT THE PALEO INTXN THE H25B MADE A 90 DEG L TURN INTO THE CRJ2. I ASKED THE H25B WHERE HE WAS GOING AND HE SAID KERNO, AN ARR FIX TO AN ARPT HE WAS NOT CLRED TO. I CHKED MY FLT DATA INFO AND IT SHOWED THAT THE H25B WAS FILED OVER AGARD FOR LGA. WHEN I TOLD THE PLT THIS, HE SAID THAT HE WAS GOING TO MMU OVER KERNO. MUCH CONFUSION FOLLOWED. I THEN TOLD THE H25B TO MAINTAIN FL200. HE WAS CLBING OUT OF FL196. THE H25B GOT TO FL203 BEFORE GOING BACK DOWN, UNDERNEATH THE CRJ2 AT FL210. THE H25B FILED 2 FLT PLANS -- 1 TO MMU AND 1 TO LGA. CLRNC DELIVERY CLRED THE H25B TO MMU BUT GAVE THE H25B THE BEACON CODE ON THE FLT PLAN TO LGA. THEREFORE, THE H25B WAS GOING TO MMU WHILE MY DATA SHOWED HIM GOING TO LGA.

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.