| 1 | SRX | Sierra Expressway Airlines | Callsign: Sierra Ex, | USA | AVCODES |
| 2 | SRX | Sierra Expressway Airlines | | | ICAO1 |
| 3 | SRX | The Seaboard Refining Co., Ltd. | 7/1930-4/1938 | | NAKINA |
| 4 | SRX | Seaboard Refining Corp. | 1/1941-4/1947 | | NAKINA |
| 5 | SRX | Sunland Refining Corp. | 1/1950 (not listed); 1/1952-10/1966; eliminated 4/1970 | | NAKINA |
| 6 | SRX | Sunland Refining Corp. | 4/38-10/66; eliminated 4/70 | | NRHS |
| 7 | SRX | SUNLAND REFINING CO. [SEABOARD REFINING CO.] | | | PWRC |
| 8 | SRXA | SPIRIT ROAD XPRESS INC | | | SCAC4 |
| 9 | SRXB | STARLITE TRANSPORTATION LLC | | | SCAC4 |
| 10 | SRXC | SUPERIOR READY MIX CONCRETE | | | SCAC4 |
| 11 | SRXD | SUPERIOR TRANSIT INC | | | SCAC4 |
| 12 | SRXF | SUPERIOR TRANSFER INC | | | SCAC4 |
| 13 | SRXG | SPARTI EXPRESS | | | SCAC4 |
| 14 | SRXH | S RT TRANSPORT LLC | | | SCAC4 |
| 15 | SRXI | SRM TRANSPORT INC | | | SCAC4 |
| 16 | SRXJ | SRRT PHOENIX LLC | | | SCAC4 |
| 17 | SRXK | STAR TAXI | | | SCAC4 |
| 18 | SRXL | SEPTEMBER TRANSPORT LLC | | | SCAC4 |
| 19 | SRXM | SUNRISE EXPRESS INC | | | SCAC4 |
| 20 | SRXN | SCARLET SEA EXPRESS INC | | | SCAC4 |
| 21 | SRXP | SUNRISE EXPRESS INC | | | SCAC4 |
| 22 | SRXQ | SOLAR TRANSPORT LLC | | | SCAC4 |
| 23 | SRXS | SMASHE | | | SCAC4 |
| 24 | SRXT | S & R TRANSPORT COMPANY | | | SCAC4 |
| 25 | SRXV | SAR TRANSPORT SYSTEMS PVT LTD | | | SCAC4 |
| 26 | SRXX | Smith R.R. Co., Inc. | 7/2005 (not listed) | | NAKINA |
| 27 | SRXX | SMITH RAILROAD CO., INC. | | | PWRC |
| 28 | SRXX | SMITH RAILROAD COMPANY INC | | | SCAC4 |
| 29 | SRXY | SITTER TRANSPORT LTD | | | SCAC4 |
