Date: 202101
Local time of day: 0601-1200
Location: MSO.Airport, MT
Weather elements / visibility: Fog; Cloudy
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Taxi
ATC / advisory: Ground MSO
Second aircraft: Light Transport
Reporter organization: Air Carrier
Reporter function: First Officer
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Human factors: Confusion; Situational Awareness
Second reporter function: Trainee; First Officer
Anomaly: ATC Issue All Types; Conflict Ground Conflict; Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: Taxi
Result: Air Traffic Control Issued New Clearance; Flight Crew Took Evasive Action
Contributing factors: Human Factors; Procedure; Weather
Primary problem: Human Factors

Narrative: Taxing from the device pad for departure we came very close to coming in contact with Aircraft Y. Aircraft Y had been given clearance to taxi to the runway while we were still finishing up de-ice and neither the Captain or myself as First Officer gave it much thought. When we finished the de-ice process I called for taxi and we were given clearance to taxi. The Runway Visual Range was being reported at the time of 1;000 ft. so the visibility was obviously a contributing factor in the described events. As we were on Taxiway A approaching an intersection; I began to notice some lights on the right hand side of the airplane. I assumed that I was seeing hangar lights as they did not appear to be moving. Looking back this was due to the fact that ourselves and Aircraft Y had roughly the same ground speed and therefore the lights were staying in the same position on my window.As we got closer the Captain and I both realized at about the same time that what we were seeing was Aircraft Y. Aircraft Y must have seen us about the same time because we both came to a stop. When we stopped on the slick taxiway we were probably no more then 20 or 30 ft. away from Aircraft Y. We began to taxi away and as we did I asked ground to verify that we were in fact cleared to taxi to the runway. They stated that we were. Aircraft Y then asked the same thing and ground replied that they as well were cleared to taxi to the same runway. Due to the 1;000 ft. Runway Visual Range I know that Tower could not see where either of us were. I think that the normal low visual procedures of reporting when passing certain points would have saved this from happening. I think that Ground thought that Aircraft Y was already at the end of the runway when we were cleared for taxi and for some reason Aircraft Y was delayed.


Second narrative: We were departing. ATIS prevailing visibility was 1/4 mile in freezing fog. After start we went to device pad 1 and completed Type I and Type IV deicing. Ground gave us taxi instructions and to hold short the ILS critical area. Taxi was uneventful until reaching an intersection. Aircraft Y had been cleared to taxi to the same runway and we nearly met at the intersection. We both applied brakes. Aircraft Y told Ground they would 'give way to...' us. After starting to taxi we called Ground to confirm our taxi instructions. Aircraft Y did the same. We were both cleared all the way to Runway 12. Aircraft Y was cleared to taxi before us and either taxied slow or delayed their start. Ground could have confirmed their position before clearing us to taxi.


Synopsis: Air Carrier flight crew reported they stopped their taxiing when they observed another aircraft taxiing into the same intersection.