| 1 | SIE | Sierra Express | Callsign: Serex, | USA | AVCODES |
| 2 | SIE | Sierra Express | | | ICAO1 |
| 3 | SIE | Siemens | | D | TRAFFIC |
| 4 | SIEA | SIERRA AGRICULTURAL TRANSPORTATION | | | SCAC4 |
| 5 | SIEB | SCHIELE ENTERPRISES INC | | | SCAC4 |
| 6 | SIEB | | City: Siegburg | D | TRAFFIC |
| 7 | SIEC | STRIVE TRANSPORT GROUP LLC | | | SCAC4 |
| 8 | SIED | Miejskie Przedsiębiorstwo Komunikacyjne w Siedlcach Spółka z o.o. | | PL | TRAFFIC |
| 9 | SIEE | SAIL GMBH | | | SCAC4 |
| 10 | SIEG | | City: Siegen | D | TRAFFIC |
| 11 | SIEH | SPIECH FARMS | | | SCAC4 |
| 12 | SIEJ | SCHIERLMAN TRUCKING | | | SCAC4 |
| 13 | SIEN | SIECOR | | | PWRC |
| 14 | SIEP | SIRACUSA MOVING & STORAGE COMPANY I | | | SCAC4 |
| 15 | SIEQ | SPEIGEL P T CO | | | SCAC4 |
| 16 | SIER | SIERRA TRANSPORT LLC | | | SCAC4 |
| 17 | SIER | Miejskie Przedsiębiorstwo Komunikacji w Sieradzu | Real: MPK, City: Sieradz | PL | TRAFFIC |
| 18 | SIES | SIDEE ENTERPRISES INCORPORATED | | | SCAC4 |
| 19 | SIESS | Siess Brennstoffe GmbH & Co KG | | AT | VKM |
| 20 | SIET | SERVICIO INTERNACIONAL DE ENLACE TE | | | SCAC4 |
| 21 | SIEU | SOMER S ISLE SHIPPING LTD | | BM | BIC |
| 22 | SIEV | SIEVEKING INC | | | SCAC4 |
| 23 | SIEX | Southern Iron & Equipment Co. | added 10/1970; eliminated 7/1972 | | NAKINA |
| 24 | SIEX | Southern Iron & Equipment Co., Division U.S. Railway Manufacturing Co. | added 7/1972; 1/1975; eliminated 7/1977 | | NAKINA |
| 25 | SIEX | Southern Iron & Equipment Co., Division Evans Transportation Co. | added 7/1977; eliminated 7/1979 | | NAKINA |
| 26 | SIEX | United States Leasing Co. | added 7/1979; 1/1980 | | NAKINA |
| 27 | SIEX | United States Railway Leasing Co. | eliminated 10/1980 | | NAKINA |
| 28 | SIEX | Southeastern Industrial Enterprises, Inc. | added 4/1995; 7/2000-7/2005; eliminated 10/2006 | | NAKINA |
| 29 | SIEX | Southern Iron & Equipment Co. | added 10/70 | | NRHS |
| 30 | SIEX | Southern Iron & Equipment Co., Division U.S. Railway Manufacturing Co. | 1/75; eliminated 7/77 | | NRHS |
| 31 | SIEX | Southern Iron & Equipment Co., Division Evans Transportation Co. | added 7/77; eliminated 7/79 | | NRHS |
| 32 | SIEX | United States Leasing Co. | added 7/79; 1/80 | | NRHS |
| 33 | SIEX | United States Railway Leasing Co. | eliminated 10/80 | | NRHS |
| 34 | SIEX | Southeastern Industrial Enterprises, Inc. | added 4/95; 7/2000 | | NRHS |
| 35 | SIEX | *UNITED STATES RAILWAY LEASING CO. [SOUTHERN IRON & EQUIPMENT CO.} | | | PWRC |
| 36 | SIEX | +SOUTHEASTERN INDUSTRIAL ENTERPRISES | | | PWRC |
| 37 | SIEX | Southeastern Industrial Enterprises | | | RSRV |
| 38 | SIEX | SOUTHEASTERN INDUSTRIAL ENTERPRISES | | | SCAC4 |
| 39 | SIEY | SIERRA SPECIALISED TRANSPORT | | | SCAC4 |
