Date: 202009
Local time of day: 0601-1200
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Descent
ATC / advisory: Center ZZZ
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; Captain
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown; Situational Awareness; Confusion
Second reporter function: First Officer; Pilot Flying
Anomaly: Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Overcame Equipment Problem
Contributing factors: Human Factors; Environment - Non Weather Related; Procedure
Primary problem: Human Factors

Narrative: While descending into ZZZ on the ZZZZZ2 STAR Landing North; unknown to me; the First Officer (PF) had gone to the PROG page of the FMC and typed in ZZZXXR on the UPDATE Selection line on the left side of the screen and selected it. He then called my attention for verification and I looked across and saw ZZZXXR on the right side of his FMC screen with an asterisk beside it. Although I do not normally put in the runway for a more accurate distance to the runway; it is commonly done by crew members that I work with. I am however not used to seeing an asterisk. Without knowing what typing had been done previously; I told him it was okay to select it. The FMC I believe then updated our position to ZZZXXR and all required points for the arrival were lost. I informed ZZZ Center that we had navigation degradation and requested vectors to ZZZ. We were given vectors and altitudes for the visual to Runway XXR and landed without further issues.Cause -1) It was the second leg of an a.m. out and back. 2) The PF had not flown as PF for quite some time and actually had picked up this trip to retain currency. 3) The PF made changes in the FMC without first alerting me. 4) I incorrectly verified that is was okay to make the selection; not knowing what entries had been made previously. 5) The entry of ZZZXXR should have been made on the line above where it was located with the asterisk. Suggestions -1) The PM should make all FMC entries when not in straight and level flight. 2) Both crew members should be aware of all FMC changes. 3) The runway entry is to be over top of the destination entry only. 4) With my being unsure about the reason for the asterisk; I should have told the PF to abandon the idea of putting in data for runway distance and leave the page.


Second narrative: While descending into ZZZ on the ZZZZZ2 STAR Landing North; I went to the PROG page of the FMC and typed in ZZZXXR on the UPDATE Selection line on the left side of the screen and selected it. As soon as I selected the incorrect LSK; I asked the Captain to take a look at the FMS; however I didn't clearly explain what I'd pressed to get there.  He saw ZZZXXR on the right side of his FMS screen with an asterisk beside it. We attempted to clear it; and enter ZZZXXR to place over the destination waypoint (ZZZ) at the correct LSK; however the command was not valid.  I asked if I should just press the LSK (Line Select Key) with the ZZZXXR and star next to it and we agreed that should clear it. Upon activating that LSK; I believe the FMC then updated our position to ZZZXXR and all the arrival points were behind us. We got a master caution and a message on the ECAM and I disconnected the autopilot and auto-throttles and continued on heading and speed for the descent.  The Captain informed ZZZ Center that we had navigation degradation and requested vectors to final for XXR. We were given vectors and altitudes for the visual to Runway XXR and landed via the visual backed up by the ILS.Cause -1) I had not flown as PF in the aircraft since June and had picked up this trip to retain currency. 2) I mistakenly entered the ZZZXXR waypoint under the wrong LSK. 3) I pressed the incorrect LSK and entered the data from the scratch-pad without confirmation from my PM and poorly communicated the nature of my error to the Captain.  4) We were unable to clear the entry through any means on the PROG page.5) We falsely concluded that pressing the LSK with the star was our only recourse.  6) Noting we had begun the descent; I should have asked the PM to accomplish this task and focus on my PF duties.Suggestions - 1) The PM should make all FMS inputs when not straight and level. 2) Both crew members should be aware of all FMS entries to include the scratch pad. 3) I continued to review FOM/FM/FTM during the several months on reserve while out of the cockpit and was primarily concerned with my proficiency at landing.  I should have gone to the training center to brush up on my FMS proficiency in addition to knowledge review.  4) I should have been more aggressive about maintaining flying proficiency; and have learned of more options that will allow me to do so in the future.


Synopsis: Air carrier flight crew reported an entry error while loading the STAR into the FMC/FMS.