Narrative:

Oklahoma city approach called me on the shout line after I accepted the hand off on aircraft X via automation. They told me that they were showing an interface failure for aircraft X; and I told them that I had taken radar on the aircraft. They told me that he would be climbing to 080. The data block of aircraft X indicated that he was VFR; and approach did not indicate that the aircraft would be IFR at 080. Upon initial contact with aircraft X; I asked him to confirm his squawk code. The code he was squawking; which he also verified when I asked; was in use by another aircraft in the ZFW system. I concluded that this was the reason that okc approach was showing an interface failure; and that I needed to put him on the code that my uret showed him being assigned. I issued the new code to the aircraft. I gave a relief briefing. During this briefing; while going over traffic in the sector; I noted to the relieving controller that aircraft X had been at or around 080 more than he had been at 085 which would have been appropriate for VFR flight. I told the relieving controller that he may want to ask him if he knew that he was at the wrong altitude for VFR aircraft. Recommendation; later in my shift; the manager called me to his desk and informed me that aircraft X had in fact been IFR for his entire flight; and explained that I should have been more inquisitive as to his curious altitude. My thought is that VFR aircraft often maneuver around their appropriate VFR altitude to stay clear of clouds. In hindsight; I could have been more proactive and queried the aircraft about his altitude.

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Original NASA ASRS Text

Title: ZFW controller described confused flight plan status event when equipment problems precluded a normal automated hand off and incorrect assumptions were made regarding an aircraft's IFR vs. VFR status.

Narrative: Oklahoma City Approach called me on the shout line after I accepted the hand off on Aircraft X via automation. They told me that they were showing an Interface Failure for Aircraft X; and I told them that I had taken radar on the aircraft. They told me that he would be climbing to 080. The data block of Aircraft X indicated that he was VFR; and approach did not indicate that the aircraft would be IFR at 080. Upon initial contact with Aircraft X; I asked him to confirm his squawk code. The code he was squawking; which he also verified when I asked; was in use by another aircraft in the ZFW system. I concluded that this was the reason that OKC Approach was showing an interface failure; and that I needed to put him on the code that my URET showed him being assigned. I issued the new code to the aircraft. I gave a relief briefing. During this briefing; while going over traffic in the sector; I noted to the relieving Controller that Aircraft X had been at or around 080 more than he had been at 085 which would have been appropriate for VFR flight. I told the relieving Controller that he may want to ask him if he knew that he was at the wrong altitude for VFR aircraft. Recommendation; later in my shift; the Manager called me to his desk and informed me that Aircraft X had in fact been IFR for his entire flight; and explained that I should have been more inquisitive as to his curious altitude. My thought is that VFR aircraft often maneuver around their appropriate VFR altitude to stay clear of clouds. In hindsight; I could have been more proactive and queried the aircraft about his altitude.

Data retrieved from NASA's ASRS site as of April 2012 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.