Date: 202001
Local time of day: 0001-0600
Location: ORD.Airport, IL
Aircraft: Regional Jet 700 ER/LR (CRJ700)
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Climb
Airspace: Class B ORD
ATC / advisory: TRACON C90
Second aircraft: Regional Jet 700 ER/LR (CRJ700)
Reporter organization: Government
Reporter function: Departure
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Situational Awareness; Communication Breakdown; Confusion
Anomaly: ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Air Traffic Control Separated Traffic
Contributing factors: Aircraft; Company Policy
Primary problem: Company Policy

Narrative: To be clear I did not have a lot going on and my complexity was not high. That is why this was a non-event. However; ORD was super busy on two runways for a little bit and I am sure the Tower was very busy landing 28C departing 28R and 22L. Ground could have also been busy so that is why I put the information in there on complexity and amount of volume. Here is what happened; we were on outboards at ORD. There were a lot of aircraft going over the airport to balance the runways. I had a strip print and an aircraft depart and tag up. It was Aircraft Z. I was waiting for this aircraft to call on. I was waiting and waiting and making a plan. Then the aircraft started climbing out of 5;000 feet; so I reached out and tried to turn the aircraft. He didn't turn or answer. I didn't know what happened or was happening. Then I did it again. I was just about to call back to the Tower and the position next to me was giving a briefing and they turned their aircraft to EARND.Aircraft X. Now they departed off of two different runways but I said to the guy next to me; 'Hey; see if you have Aircraft Z by chance.' He did. So somehow Aircraft Z going westbound departing off of Runway 28R was on the same frequency as Aircraft X departing off of Runway 22L. When the instruction for Aircraft X was given; Aircraft Z and Aircraft X took it. The Controller said he didn't hear any indication that there was a step on each other or anything. During this time Aircraft Y also had departed and went to the incorrect frequency and that Controller had to send him to the correct frequency. So there were 3 similar sounding aircraft on 1 frequency when only two were supposed to be there and they were all climbing when only two were supposed to be. We have tried to explain how bad incorrect frequency transfers could be and have kept records for months but it seems there is no sense of urgency at how bad this could be. The two aircraft came within approximately 4 miles from each other with one climbing blindly. That was very lucky.My recommendations would be to track these incidents when similar sounding aircraft are on the same frequency so that it can be brought to the airline dispatchers' attention and show the replay on what could happen and why they should be aware of the issue. However; when I have brought these things recently to our supervisors in the room; they have been advised that they should not keep track of things like this by [the] upper management Operations managers and higher. They tell us we should report it when they could report it just like I can. This was luck this time that nothing happened. So I guess we will just open that Swiss cheese holes with negligence and laziness and I will be in the seat one day when two planes come together and I may not be lucky like this time to be able to listen to the person next to me give the briefing. Or we can go back to due diligence; attentiveness; and caring and report things like this and care about the operation. Put effort on everyone's end to know when similar call signs are on frequencies or multiple frequencies. Demand that Dispatch works hard to not use call signs like this. Or not; who cares any more right.




Synopsis: A TRACON Departure Controller reported two aircraft flew dangerously close conflicting courses due to one aircraft taking the instruction of another aircraft with a nearly identical call sign departing at the same time.