Date: 201706
Local time of day: 1801-2400
Location: BOS.Airport, MA
Flight conditions: VMC
Light: Daylight
Aircraft: Small Transport; Low Wing; 2 Recip Eng
Operator: Air Taxi
Operating under: Part 135
Flight plan: IFR
Mission: Passenger
Flight phase: Takeoff / Launch
ATC / advisory: Tower BOS
Second aircraft: B737 Undifferentiated or Other Model
Reporter organization: Government
Reporter function: Local
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Confusion; Situational Awareness; Communication Breakdown
Second reporter function: First Officer; Pilot Not Flying
Anomaly: ATC Issue All Types; Conflict Ground Conflict; Critical; Deviation / Discrepancy - Procedural Clearance; Ground Incursion Runway
Detector: Person Flight Crew; Person Air Traffic Control
When detected: Taxi
Result: Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Air Traffic Control Separated Traffic; Flight Crew Became Reoriented; Flight Crew Returned To Clearance; Flight Crew Requested ATC Assistance / Clarification; General Flight Cancelled / Delayed
Contributing factors: Human Factors; Procedure
Primary problem: Human Factors

Narrative: I cleared Aircraft Y for takeoff. I instructed Aircraft Z to line up and wait. Holding short at an intersection was Aircraft X. While Aircraft Y was commencing departure roll; Aircraft X began to line up and wait at the intersection. I immediately told Aircraft X to stop and cancelled the takeoff clearance of Aircraft Y who was aborting takeoff at the same time. We had just completed the fourth runway change of the shift and were in departure delays of more than 30 minutes. Gate holds were in effect and it was a high volume; high complexity environment. Nobody realized that the similar sounding call signs existed. Had it been caught and the procedures applied; I don't believe this incident would have happened. I don't have any recommendations. If anyone had realized that the similar call signs were there; the strips would have been marked accordingly and everyone would have been made aware of the situation.


Second narrative: On our taxi to depart; the winds shifted to favor a different runway. With that being said all of the traffic was given new taxi instructions to change runways. We were given the new runway at an intersection. Once we were the next in line to depart we heard tower clear us to line up and wait. I read the clearance back to the tower and we started rolling. My Captain and I thought that it was suspicious that we were given this clearance because Aircraft Y had just been given the clearance to line up and wait. They were also asked if they could maintain visual separation from the traffic who had just departed. With that being said I thought it could be possible that they were trying to depart us before Aircraft Y; because they were trying to clear up the traffic jam that was taking place. As we rolled over the hold short line; I saw that Aircraft Y had their lights on and relayed that information to the Captain. At this point the pilot came to a complete stop; short of the runway but over the hold short line. Due to this Aircraft Y aborted their takeoff and both of us were instructed to taxi down the road and exit. At this point the incident was over.After landing at our destination we reviewed the recordings and realized Aircraft Z; the same [flight] number as my Captain's had been cleared to line up; yet the [carrier] part of the transmission had been blocked. We simply heard our number and line up and wait. The tape is very garbled; giving me reason to believe the tower did not catch which airline called back but heard the same number. It is clear to me now that I was at fault for this incident. I should have been more vigilant and should've asked for clarification if there was any doubt in my gut.


Synopsis: A Tower Controller and two associated pilots reported a ground conflict and runway incursion due to an aircraft that taxied over the hold bars due to similar callsigns.