Narrative:

Aircraft X was told runway 27L taxi into position and hold; readback was fine. 2 minutes later; aircraft X runway 27L cleared for takeoff (fly heading 220 degrees). Aircraft X reads back 'aircraft X cleared for takeoff heading 320 degrees. I then key up and say 'heading 220 degrees.' he said 'ok; I had it right the first time; heading 220 degrees.' then I get the readback again; saying 'aircraft X runway 27L cleared for takeoff heading 220 degrees.' I think that this is the pilot just correcting himself and saying it the proper way. Turns out; this is the second guy reading back the clearance. By this time; we have hollering and screaming going on in the tower with people saying this guy took off from our runway without a clearance. Aircraft Y departed runway 35R on the departure clearance that I gave to aircraft X off of runway 27L. Aircraft Y was on the wrong local frequency; he never checked in. When he flipped over to my frequency; he heard me say 'aircraft X runway 27L cleared for takeoff; fly heading 220 degrees' and he (aircraft Y) immediately read this back 'aircraft Y cleared for takeoff heading '320' degrees.' I said 'no; 220 degrees;' then he and the right aircraft both read it back. The first guy read it back incorrectly and then the second pilot read it back correctly. So it sounded to me like the pilots were in the same plane -- one pilot read it the wrong way and then maybe his copilot corrected him and read it back the right way. This was not the case though -- 2 pilots in 2 different planes took off on 2 different runways at phl on one clearance.

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Original NASA ASRS Text

Title: PHL controller described an unauthorized takeoff when two same company aircraft with similar sounding four-digit flight numbers and readbacks became confused; one taking off without a clearance.

Narrative: Aircraft X was told Runway 27L taxi into position and hold; readback was fine. 2 minutes later; Aircraft X Runway 27L cleared for takeoff (fly heading 220 degrees). Aircraft X reads back 'aircraft X cleared for takeoff heading 320 degrees. I then key up and say 'heading 220 degrees.' He said 'OK; I had it right the first time; heading 220 degrees.' Then I get the readback again; saying 'aircraft X Runway 27L cleared for takeoff heading 220 degrees.' I think that this is the pilot just correcting himself and saying it the proper way. Turns out; this is the second guy reading back the clearance. By this time; we have hollering and screaming going on in the Tower with people saying this guy took off from our runway without a clearance. Aircraft Y departed Runway 35R on the departure clearance that I gave to Aircraft X off of Runway 27L. Aircraft Y was on the wrong Local frequency; he never checked in. When he flipped over to my frequency; he heard me say 'aircraft X Runway 27L cleared for takeoff; fly heading 220 degrees' and he (Aircraft Y) immediately read this back 'aircraft Y cleared for takeoff heading '320' degrees.' I said 'No; 220 degrees;' then he and the right aircraft both read it back. The first guy read it back incorrectly and then the second pilot read it back correctly. So it sounded to me like the pilots were in the same plane -- one pilot read it the wrong way and then maybe his copilot corrected him and read it back the right way. This was not the case though -- 2 pilots in 2 different planes took off on 2 different runways at PHL on one clearance.

Data retrieved from NASA's ASRS site as of May 2009 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.