Date: 201810
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Aircraft: Medium Transport; Low Wing; 2 Turbojet Eng
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Takeoff / Launch
ATC / advisory: Tower ZZZ
Reporter organization: Government
Reporter function: Local
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Communication Breakdown
Second reporter function: Pilot Flying; Captain
Anomaly: ATC Issue All Types; Conflict Ground Conflict; Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Person / Animal / Bird; Ground Incursion Runway
Detector: Person Air Traffic Control
Result: Air Traffic Control Issued New Clearance; Flight Crew Rejected Takeoff
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: I was working both locals combined during the planning stages of a runway change. We were on a west operation landing runway XXR and runway XY. We were going to go to runway XXL and runway YY and I was informed of the last XXR arrival. An aircraft reported hitting a fox on runway XXR which closed the runway and I sent the first guy around on final and was able to side step the rest of the arrivals to runway XXL. I had 2 departures for XXL; I cleared the first one in between arrivals and the second one was Aircraft X. Since we were going to be departing runway XXR soon; ground control was instructed to start taxiing aircraft to runway XXR which was closed at the time due to the fox being hit. After an arrival touched down I told Aircraft X to line up and wait. He did just that; but subsequently Aircraft Y [similar callsign to Aircraft X] took runway XXR. The supervisor must have taken the closed runway X's off the runway because I never recalled the airport releasing the runways back to the tower. I cleared Aircraft X for takeoff on runway XXL and both aircraft started rolling. I immediately told Aircraft Y to stop and exit the runway and told Aircraft X he could roll. Both aircraft slowly exited the runway and the next arrival for runway XXL was sent around. I do not have any recommendations for this event; they were similar sounding call signs but the one concern I had was why would the supervisor take the X's off the runway if the runway was still closed which would dismantle that feature of the safety logic. Luckily I was able to stop Aircraft Y from taking off of a closed runway.


Second narrative: On Aircraft Y from ZZZ to ZZZ1 on the take-off roll phase. While lined up and waiting for the take-off clearance on runway (XXR) the tower says 'Aircraft Y clear for take-off runway XXL.' By the time he finished his sentence I was already rolling. As the pilot flying at the time; I initiated the take-off roll; but when I realized he said XXL - and as the FO (First Officer) was trying to clarify what he said - I rejected the take-off roll and got off the runway; then tried to clarify what happened and called Dispatch to let them know the situation. So; it turns out that there was another [Company] aircraft with similar call sign (Aircraft X) lined up and waiting on runway XXL; and the controller got confused between us and their call sign and runway assignment. After all of the stuff cleared out we went back to the runway and took off with no issues. On my behalf I should've waited until the controller finished his complete clearance before I initiated the take-off roll. Confusing take off instruction. Acted little too early before clarifying the clearance instruction. Rejected take-off. Listen until the complete ATC clearance is issued then act.


Synopsis: Tower Controller and Air Carrier Captain reported taking closed runway resulting in RTO due to similar callsign with another aircraft.