Date: 201510
Local time of day: 1801-2400
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Light: Night
Aircraft: A320
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Second aircraft: Commercial Fixed Wing
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; First Officer
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Confusion; Distraction; Situational Awareness; Communication Breakdown
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance
Detector: Person Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented
Contributing factors: Company Policy
Primary problem: Company Policy

Narrative: On this event we were call sign Air Carrier XXY; we were cruising at 37000 feet. We were on ARTCC frequency. Due to the late hour we requested to be rerouted. We were told to contact [next] ARTCC.We checked in with the controller and made our request for the reroute. The controller then cleared us. The controller finished the transmission calling us Air Carrier XYY and stated to maintain 36000 feet. We read back the clearance and emphasized our call sign. We also said 'Descending from 37000 feet to maintain 36000 feet.' The controller gave no further response and did not make any correction. We entered the reroute into the MCDU and descended to 36000 feet.A few minutes later we were told to contact [previous] ARTCC which was the previous frequency we were on. Just as we were about to switch; Air Carrier XYY checked in on frequency and the controller began getting confused and asked if they were proceeding to [fix]. They seemed also confused and said they didn't request any changes. At that time we started wondering about our clearance. We asked the controller if they were certain they wanted us to switch to ARTCC and she responded with an affirmative.When we checked in with ARTCC I asked the controller to verify that we were on the right frequency and that we had indeed received the clearance to [fix] and [fix]. The controller returned a minute or two later saying that we were okay. We followed Air Carrier XYY the rest of the way into the airport and when we tuned into the last TRACON frequency we were also joined by Air Carrier XZY bringing the total of 3 company planes with similar call signs on the same frequency. The last controller on ARTCC asked that I inform the company to change the flight numbers and that it is unacceptable to have so many call signs so close together heading to the same place on the same type of plane at the same time. We were on time so unless the other flights were delayed it appears her concern is valid. At no prior point was Aircraft Y on the same frequency with us and we never suspected any issues prior to this moment. We also did not receive any warning from ARTCC that there was similar call signs on the frequency. The Center Controller suggest that we have vastly different call signs with something else to distinguish us better. I also suggest we stop filing similar call signs during the same time periods.




Synopsis: On a particular route to an airport aircraft of the same company with similar call sign numbers arrive simultaneously causing confusion.