Date: 201212
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Aircraft: Regional Jet 700 ER/LR (CRJ700)
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Taxi
ATC / advisory: Tower ZZZ
Reporter organization: Government
Reporter function: Ground
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Communication Breakdown; Confusion; Situational Awareness
Second reporter function: Local
Anomaly: ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control
Result: General None Reported / Taken
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: I was opening up Ground Control position. I had an aircraft call me and I missed the call sign; so I asked; 'Was that Air Carrier ABCD that called?' The aircraft answered; 'Affirmative.' I noticed on the ASDE-X that the aircraft only had a beacon code showing that was associated with another aircraft I had in the 'awaiting to taxi' bay. I told the pilot of (who I thought was Air Carrier ABCD) that he was squawking companies call sign. The pilot said; 'Oh thank you I was wondering about that.' I thought that the aircraft Air Carrier ABEF may have gotten his clearance at or around the same time as Air Carrier ABEF; and he had just mixed up his squawk with his company's call sign. So I told him to squawk whatever code I had for Air Carrier ABCD; because that's who I thought he was. When we listened to the tape; he originally called with the correct call sign of Air Carrier ABEF; I had missed that call; and asked if that was Air Carrier ABCD who called and he said 'affirmative.' That's how I ended up giving him the squawk of Air Carrier ABCD. The ASDE-X showed no indications of a 'dupe beacon' which; it will do if 2 aircraft are on the same squawk. So I thought everything was fine at that point and the issue was resolved. I did not use his call sign when I switched him to Tower because he was the only aircraft on my frequency at that time. He did not read back a call sign when given the switch to Tower either. That was my fault. I should have; and always do; use a call sign; I'm not sure why I did not that time. When the aircraft was on the runway; the Local Controller cleared him for take off and only noticed the call sign difference when the aircraft was switched to Potomac TRACON; to which then; the Local Controller called over to the Departure Controller and fixed the issue. After listening to the Local Controller on the tape; the aircraft used his correct call sign of Air Carrier ABEF when they read back the take off clearance and the Local Controller did not catch the call sign error at that time. I will be and have been since; VERY careful about aircraft call signs; squawk codes and read backs. I could have done more of an investigation on the aircraft since they were squawking another aircraft's call sign and asked their destination. I am aware of how things can get confused and I have realized how important it is to make sure call sign and squawk are correctly associated with aircraft ID.


Second narrative: Assigned Local Control 1; overheard Ground Control 1 in discussion with pilot about wrong beacon code and call sign. ASDE-X displayed data tag of Air Carrier ABCD at Runway 19L. I cleared Air Carrier ABCD for takeoff Runway 19L. When I shipped Air Carrier ABCD to departure; I noticed he read back Air Carrier ABEF. I glanced at ASDE-X and confirmed the tag said Air Carrier ABCD. I made a quick comment to Ground Control 1 that the guy was still messing up his call sign. Moments later; the Sector at ZZZ TRACON called to question the identity of Air Carrier ABEF. They said Air Carrier ABCD was actually ABEF. He had tagged up as Air Carrier ABCD. I found the flight progress strip of Air Carrier ABEF and scanned the strip. I asked them to double confirm the aircraft's destination and they confirmed it was Air Carrier ABEF to [the correct destination]. I advised Supervisor we had a possible communication/call sign issue and that somewhere along the line some mistakes had been made on both sides. Supervisor listened to tapes from both Ground Control 1 and Local Control 1. Local Control 1 (me) issued takeoff clearance to Air Carrier ABCD and it was read back by Air Carrier ABEF; I missed the bad call sign. On shipping to Departure I caught the bad call sign but attributed it to the pilot because of the information Ground Control 1 gave to me. On review of Ground Control tapes the pilot called for taxi and the Ground Control 1 missed call sign. Ground Control 1 asked 'is that Air Carrier ABCD?' to which pilot said yes. A conversation ensued because he was actually squawking ABEF. Ground Control 1 joked that he was squawking companies call sign and assigned him the beacon code of Air Carrier ABCD. There is where the confusion started. The ASDE-X now said Air Carrier ABCD. No other call signs were used in the conversation between pilot and ground. Pilot called and had discussion with Supervisor after Center asked him to call. I missed the read back on the takeoff clearance. Pilot was not vigilant either and he never questioned that ATC was calling him Air Carrier ABCD. Remain focused at all times. In the event a situation is unusual be extra vigilant! Remind pilots that they should question call signs and anything that seems out of place!


Synopsis: Multiple Air Traffic controllers and an Air Carrier Captain described a confused clearance and call sign event that resulted in an unsafe condition with several controllers confused as to the identity and route of an IFR departure.