Cessna 310/T310C
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (mon) 7
Situational Awareness; Confusion
ATC Issue All Types; Airspace Violation All Types; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Provided Assistance
ATC Equipment / Nav Facility / Buildings; Human Factors; Procedure
I came on Position to open North departure. Within a minute or two I called the satellite controller to consolidate all of satellite (G;K;E) at D. This is a usual procedure for this time of night. During the briefing the relieving controller briefed that the only traffic on frequency was [Aircraft Y]; the call sign of which I cannot remember. The other aircraft in our air space was [Aircraft X] that was only a few miles from the boundary of our airspace and sector 5's airspace at ZMP.  I took this to mean that since [Aircraft X] was not on frequency a handoff had been completed and radio communications transferred. After I consolidated the positions; I adjusted my scope and moved tags around. At that time I noticed that [Aircraft X] was still on our D tag and not on a center's C tag. However; I didn't think too much of it because it happens often that the center will make adjustments to the flight plan while an aircraft is still in our space. If a controller moves the tag or otherwise clicks on the target it will revert to the initial controller's tag. In this case a D. I did check the audio recording after the incident and the relieving controller did in fact say that the only aircraft on frequency was [Aircraft Y]; and not [Aircraft X].  However; unbeknownst to me at the time; [Aircraft X] was on frequency and a handoff had not been accomplished. [Aircraft X] then flew into Sector 5's airspace; at which point I terminated the track about 7 miles from my boundary. Sector 5 came on the shout line indicating that [Aircraft X] was in their space and that they had not taken the handoff. I initiated a verbal handoff and transferred radio communications to sector 5 when the aircraft was approximately 10 miles inside their airspace.  Sector 5 then request I 'flash' the data block to them; but I was unable to since I had dropped the tag. If ZMP changes to the flight plan of an aircraft in our airspace didn't cause the identifying tag to revert to the initial controllers symbol; i.e.; a 'D' tag; when we moved the data block; then that would help eliminate confusion about an aircraft's handoff status.
M98 controller reports of receiving a briefing that the relieving Controller said there was only one aircraft on the frequency. Controller observed another aircraft in the airspace; and Controller assumed it had been handed off and communications transferred. The aircraft was on a different tag so this also led the Controller to think it had been handed off. The aircraft was found to be on the reporters frequency and ended up violating the Center's airspace without a handoff. Possible related issue was someone possibly had changed the data tag; and this showed the Controller that it was someone else's aircraft.