Date: 201511
Local time of day: 0001-0600
Location: DFW.Airport, TX
Flight conditions: Marginal
Light: Daylight
Aircraft: Regional Jet 900 (CRJ900)
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
Airspace: Class B DFW
ATC / advisory: TRACON D10
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Second reporter function: Captain; Pilot Flying
Anomaly: ATC Issue All Types; Conflict Airborne Conflict; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Automation Aircraft RA; Automation Aircraft TA; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Air Traffic Control Issued Advisory / Alert; Flight Crew Took Evasive Action; Flight Crew Returned To Clearance; Flight Crew Became Reoriented
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: During our descent on the BOOVE3 Arrival; we were given instructions to descend via and given runway 17C into DFW. I believe we were around DELMO when we were given some ATC instructions. I was the pilot not flying and was getting updated ATIS information so I am not sure what the instructions were. I believe my Captain thought he heard ATC instructions to descend to 5000 feet on 210 KIAS. When I got off the radio TCAS announced traffic and I was looking to see where the traffic was. Shortly after that the Captain asked ATC to verify our descent instructions to 5000 feet. ATC replied negative; climb immediately to 11000 feet. The Captain turned the auto pilot off and initiated a climb immediately. Shortly after that TCAS started issuing instructions to climb immediately; which we already climbing per ATC instructions. Prior to all that ATC had alerted us that there was another aircraft; [different company but same flight number] on the approach frequency. I believe the Captain thought he heard our company name but it seems the descend information was for the other company. I thought I heard him repeat the descent instructions to ATC as we always do and since he was not corrected; thought he gotten the instructions for our flight.A few minutes later; ATC contacted us and gave us a phone number to give DFW Approach Control a call to discuss a possible pilot deviation.I would say when there are two similar call signs; pilots should be extra vigilant and make sure ATC instructions are for their aircraft. Also if a pilot is off the radios and did not hear the last ATC instructions that involves a climb or descent; they should query ATC for the last instructions to ensure both pilots are on the same sheet of music.


Second narrative: The incident started when approach advised that there was another company with the same flight number on frequency. Descending on the BOOVE THREE RNAV ARRIVAL near the MOWWW intersection while the First Officer was on a separate frequency listening to ATIS I heard ATC instructions to 'slow 210 knots then descend to 5000 feet.' I then complied with said instructions. Shortly after an aircraft appeared on TCAS to be at approximately 10;000 feet. I then asked the controller if we were cleared down to 5000 feet. He quickly responded 'negative climb immediately to 11;000 feet.' I complied. Soon after we received a TCAS RA and continued the climb back to 11000 feet where we were clear of conflict. Before approach handed us off to tower we were asked to call a phone number regarding a possible pilot deviation. It seems evident that I followed ATC instructions for a different aircraft. I should have been more diligent in verifying ATC instructions as there were two aircraft with same flight numbers on frequency. I also should have asked my First Officer to stay on frequency as we were in a high traffic environment. In future flying I will be more aware of the increased potential for confusion in these situations.


Synopsis: CRJ-900 flight crew reported taking the clearance of another company's flight with the same flight number and descending below their assigned altitude. This resulted in a TCAS RA.