Date: 202007
Local time of day: 0001-0600
Location: ZZZ.Airport, US
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Taxi
ATC / advisory: Tower ZZZ
Second aircraft: Commercial Fixed Wing
Reporter organization: Air Carrier
Reporter function: First Officer
Reporter qualification: Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Human factors: Confusion; Situational Awareness; Communication Breakdown
Second reporter function: Captain
Anomaly: ATC Issue All Types; Deviation / Discrepancy - Procedural Clearance; Ground Incursion Runway
Detector: Person Air Traffic Control
When detected: Taxi
Result: Air Traffic Control Issued New Clearance; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Procedure; Human Factors; Staffing
Primary problem: Procedure

Narrative: While preparing to depart Runway XXR out of ZZZ; [on] Flight ABCD; [we] experienced an inadvertent miscommunication with Tower Control. Being the only aircraft holding short of XXR; our crew misheard the call sign as Tower cleared for takeoff the only departing traffic on XXR.  In this miscommunication; Flight ABCD repeated the instruction  'Flight ABCD; cleared for takeoff; Runway XXR'. No contrary command was then given by Tower. While aligned on the runway and preparing to depart; Tower requested a radio check; followed by instructions to hold short of XXR. Our crew responded in kind; notifying Tower that we were on the runway. At this time we also queried if Tower would like us to exit the runway. Tower then cleared us for takeoff with no further issue before handing us off to Departure. Miscommunication was likely due to both our misunderstanding the initial call sign and Tower Control operating numerous frequencies with multiple departing runways. Extra vigilance on our part in verifying ALL call signs/instructions. Awareness of ATC threats through reduced staffing and managing multiple frequencies.We understand the breakdown in communication that occurred and the need for vigilance in clarifying any future instructions or questions.


Second narrative: Taxiing out to Runway XXR we hear a radio call from Aircraft Z on several mile final for XXR. We then hear a takeoff clearance for Runway XXR that we believed to be for us. '.... cleared for takeoff Runway XXR; Aircraft Z on a 3 mile final.' Our response 'Cleared for takeoff Runway XXR; Flight ABCD.' (I listened to the audio after the flight and it turned out the Tower Controller initially said 'Flight EFGC cleared for takeoff Runway XXR Aircraft Z on a 3 mile final.') We obviously did not know that in the moment. The problem with that was we knew Flight EFGC was holding short of Runway XXL at B5 awaiting takeoff clearance. We were number one for departure off Runway XXR and all instructions from Tower were directed towards our situation as we saw Aircraft Z on a 3 mile final for Runway XXR. Once we were on the runway aligned with the centerline; Tower asked for a radio check. We responded. Then we hear 'Flight ABCD hold short of XXR'. We queried Tower that we had been cleared for takeoff and already positioning on XXR. Tower cleared us for takeoff XXR with no further incident.I think Tower was having some miscommunication on multiple Tower frequencies or multiple aircraft on multiple runways. Tower had no further comments or questions when handing us off to Departure and nothing indicated there was any sort of problem other than a brief miscommunication that was quickly resolved. Safety was never compromised. Seems as if Tower just used the wrong call sign when clearing the aircraft holding short of XXR (which was us) for takeoff that we inadvertently missed initially; but was quickly resolved with a query back and forth with ATC.Always a good idea to verify and be fully aware of call sign and instructions. We know going forward with staff reductions ATC can be a threat. We understand the breakdown in communication and know what we would do differently next time.


Synopsis: Air carrier flight crew reported a runway incursion which resulted from a call sign misunderstanding. A contributing factor was that the Tower Controller was managing multiple frequencies and runways.