| 1 | SMO | Servicios Aereos Automotriz, S.A. de C.V. | Callsign: Serviautomotriz, | MEX | AVCODES |
| 2 | SMOB | SMITH MOTOR FREIGHT INC | | | SCAC4 |
| 3 | SMOC | STERLING MOVING & STORAGE INC | | | SCAC4 |
| 4 | SMOD | SERV MOD DE TRANSPORTACION EL AGUIL | | | SCAC4 |
| 5 | SMOE | SMITH, HAROLD EUGENE | | | SCAC1 |
| 6 | SMOI | STEARNS MOVING & STORAGE OF KOKOMO | | | SCAC4 |
| 7 | SMOK | SMOKETREE INC. | | | SCAC4 |
| 8 | SMOK | Svenska Motorvagnsklubben | | SE | VKM |
| 9 | SMOM | SUMMIT OIL COMPANY LLC | | | SCAC4 |
| 10 | SMONM | Santa Monica Municipial Bus Lines | | USA | TRAFFIC |
| 11 | SMOP | SEMO EXPRESS LLC | | | SCAC4 |
| 12 | SMOR | SEMINOLE EXPRESS | | | SCAC4 |
| 13 | SMOU | LLC SPECIAL MAINING SOLUTIONS | | UA | BIC |
| 14 | SMOU | AIR LIQUIDE MAROC | | | SCAC4 |
| 15 | SMOV | SERVICIOS MOVI | | | SCAC4 |
| 16 | SMOX | Standard Molasses Co. | 1/1952-7/1954; eliminated 10/1957 | | NAKINA |
| 17 | SMOX | Standard Molasses Co. | 1/52; eliminated 10/57 | | NRHS |
| 18 | SMOX | STANDARD MOLASSES CO. | | | PWRC |
| 19 | SMOY | SMITH OIL COMPANY | | | SCAC4 |
