Date: 201209
Local time of day: 1201-1800
Location: ORD.Airport, IL
Flight conditions: VMC
Light: Daylight
Aircraft: EMB ERJ 145 ER/LR
Operator: Air Carrier
Operating under: Part 121
Mission: Passenger
Flight phase: Climb
Airspace: Class E ZAU
ATC / advisory: Center ZAU
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown
Anomaly: ATC Issue All Types; Deviation / Discrepancy - Procedural Clearance
Detector: Person Flight Crew
When detected: In-flight
Result: General None Reported / Taken
Contributing factors: Company Policy
Primary problem: Company Policy

Narrative: Initial departure was normal and we were vectored to a heading of 080. Chicago Departure Control (125.0) told us to contact Chicago Center on 120.35 which my First Officer read back with our call sign (Air Carrier XXXX). My First Officer checked in with Chicago Center as (Air Carrier XXXX). The Controller directed us to turn to a heading of 360 and climb to FL190 which my First Officer read back to include (Air Carrier XXXX). A few minutes later we were handed off to another Chicago Center frequency where we checked in with (Air Carrier XXXX). The Controller; using (Air Carrier XXXX); cleared us to the CWA via an intersection then direct to the airport. My First Officer read the clearance back (with Air Carrier XXXX). I told my First Officer that clearance can't be correct and ask for a clarification which he did. The Controller gave us the same clearance. This time I told the Controller (Air Carrier XXXX's) destination. There was a pause. Then the Controller said the previous clearance was for (Air Carrier XXYX) and we should return to our previous frequency. We attempted to contact Chicago Center on 120.35; but got no response. At this time; I took us back to 125.0 (Departure) and my First Officer checked back in as (Air Carrier XXXX) and said we were handed off incorrectly. The Controller instructed us to turn to a heading of 090 and climb to 16;000 FT. At the time we were climbing through 12;500 FT. Following the new vector; we proceeded to our destination without further complications. Throughout this mis-communication event; I didn't hear (flight XXYX) on any of the ATC frequencies. Because; when we initially received the heading of 360; I was a bit suspicious something wasn't right. However; my suspicions were suppressed when several radio calls were answered with (Air Carrier XXXX). I then thought the heading was for traffic. During the past 18 months or so; I have noticed two things about call signs and ATC. First; our company has a lot of flights with similar call signs (only one digit difference) in the same airspace at once. This leads to numerous read back/call back errors (I note an average of about 3/trip). Second; ATC will mix-up a call sign (transposing digits in a flight number or using an incorrect digit) where it is normally caught by the aircrew. Our Company is not the only carrier this happens to. Suggestions; with my initial suspicion that the Controller might have us on frequency in error; we should have verified to the Controller that he was talking to.




Synopsis: Air Carrier with ZAU described a very confused communications event involving four digit call signs and attempts to communicate with ATC.