Narrative:

I issued taxi instructions air carrier XXXX to runway 1L via a/F1/B. The instructions were read back to me. I later told air carrier XXXX to monitor the other ground frequency and received acknowledgement. At no time did air carrier XXXX tell me that I was calling them the wrong call sign and that their actual call sign is air carrier yxyx. To my knowledge; the controller working the frequency did not get corrected by the pilots of air carrier yxyx; either; nor did the local controller when 'air carrier XXXX' was told to line up and wait. Air carrier XXXX's flight plan was removed from the system while they were believed to be holding on the runway and the announcement was made to them that a new flight plan was being worked on and that they were to hold in position. Once again; no correction was made by the pilots about the wrong call sign. Air carrier XXXX was a Porte3 departure; hence why I originally issued them taxi instructions to runway 1L. Air carrier yxyx was a SFO8 departure. It was not known that air carrier XXXX was actually air carrier yxyx until the aircraft was observed turning right instead of left and local control questioned the pilot. Behind them on departure also was a B737; airborne; on a SFO8 off of 1R. I recommend a procedure change on air carrier XXXX's part with their similar sounding call signs. Those call signs are too close and almost caused a catastrophe.

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Original NASA ASRS Text

Title: SFO Controller described a confused flight plan event where an aircraft's call sign was mixed up during the taxi out to the departure runway. The reporter listed company similar sounding call signs as contributing to the incident.

Narrative: I issued taxi instructions Air Carrier XXXX to Runway 1L via A/F1/B. The instructions were read back to me. I later told Air Carrier XXXX to monitor the other Ground frequency and received acknowledgement. At no time did Air Carrier XXXX tell me that I was calling them the wrong call sign and that their actual call sign is Air Carrier YXYX. To my knowledge; the controller working the frequency did not get corrected by the pilots of Air Carrier YXYX; either; nor did the Local Controller when 'Air Carrier XXXX' was told to line up and wait. Air Carrier XXXX's flight plan was removed from the system while they were believed to be holding on the runway and the announcement was made to them that a new flight plan was being worked on and that they were to hold in position. Once again; no correction was made by the pilots about the wrong call sign. Air Carrier XXXX was a Porte3 departure; hence why I originally issued them taxi instructions to Runway 1L. Air Carrier YXYX was a SFO8 departure. It was not known that Air Carrier XXXX was actually Air Carrier YXYX until the aircraft was observed turning right instead of left and Local Control questioned the pilot. Behind them on departure also was a B737; airborne; on a SFO8 off of 1R. I recommend a procedure change on Air Carrier XXXX's part with their similar sounding call signs. Those call signs are too close and almost caused a catastrophe.

Data retrieved from NASA's ASRS site as of July 2013 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.