Date: 201807
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: Regional Jet 900 (CRJ900)
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class B ZZZ
ATC / advisory: TRACON ZZZ
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Human factors: Communication Breakdown; Situational Awareness
Second reporter function: Pilot Not Flying; Captain
Anomaly: Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: We set the aircraft up for an approach to XXR. Once on with Approach we got changed to XXC. We got the numbers; rebriefed the approach; and set the new nav freq. We got cleared to join XXC approach and joined XXR by mistake. Once ATC asked if we joined the center we realized what had happened. I kicked the autopilot off while the captain fixed the problem and we moved over to the center outside of ZZZZZ. The flight continued with no further occurrences. What happened was in the approach phase of flight we became task saturated with switching everything and the captain forgot to change the runway in the FMS and I forgot to make sure he did it. ATC did not issue a phone number. And no other aircraft had to deviate because of our mistake.


Second narrative: In a CRJ-900; FO (First Officer) leg; on ZZZZZ inbound; expecting; briefed and set up for XXR knowing we may; of course; get a different runway. Upon checking on with Approach; we were given XXC so we proceeded to get set up for that. I put the new frequencies in the standby but forgot to switch the approach in the FMS. When the time came; we were both expecting the Aircraft to swap from white to green needles on its own and it did- except that XXR was still in the FMS so when it did automatically swap we didn't notice that it was not to the runway to which we were cleared.No sooner had we joined the LOC when ATC queried us asking if we had lined up with XXR. Then; without waiting for an answer; he gave us a heading and asked if we could still cross ZZZZZ as his clearance (which I/we had accepted moments before) required. The FO disconnected the auto pilot and turned left; I set up his heading and he called for HDG mode. I quickly put XXC in the FMS; we confirmed and we got the AC in approach mode; joining at ZZZZZ without further incident. ATC called when he saw us join the R side. Never replaced XXR with XXC in the FMS; the 900 automatically joined and swapped to green needles to the runway that was IN THE FMS. We had passed abeam the last fix on the arrival and; therefore; 'cleaned it up and made it big' BEFORE we became aware of the runway 'change' so we missed that opportunity to catch the fact that we were looking at the wrong fixes. I honestly don't know if I consciously was aware of this at the time but; in the NG; the green to white needle auto swapping function on an ILS is dependent on what approach is loaded in the FMS. What frequency is currently in the standby; as far as it's concerned; is irrelevant. FO switched the autopilot off; hand flew the newly assigned intercept heading while I 'fixed' the FMS. We joined the correct localizer. Even if we're past all the fixes on the arrival; maybe don't 'clean it up and make it big' until we actually KNOW our runway. That will call attention to the FMS which may have prevented this.


Synopsis: CRJ-900 flight crew reported lining up for the wrong runway.