| 1 | SM | Sunworld International Airlines, Inc. | ICAO: SWI, Callsign: Sunworld, IATA Prefix: 375, Designator SM recalled by IATA | USA | AVCODES |
| 2 | SM | Peregrine Air Services Ltd. d/b/a Aberdeen Airways | ICAO: AAW, Subsidary of Air Provence | GB | AVCODES |
| 3 | SM | Altair Linee Aeree S.p.A. | ICAO: SMI, Callsign: Sierra Mike, Ceased Operations | I | AVCODES |
| 4 | SM | Air Ecosse Ltd | ICAO: ECS, Callsign: Ecosse Air, Founded in 1977 | GB | AVCODES |
| 5 | SM | Southend Municipal Flying School | Callsign: Scofly, | GB | AVCODES |
| 6 | SM | Swedline Express AB | ICAO: SRL, Callsign: Starline, IATA designator changed from T9*. Name changed from AB Varmlandsflyg w.e.f. 01 December 2002. | S | AVCODES |
| 7 | SM | Spirit of Manila Airlines Corp | ICAO: MNP, Callsign: Manila Sky, IATA Prefix: 976, | RP | AVCODES |
| 8 | SM | Air Cairo | ICAO: MSC, IATA Prefix: 381, IATA designator changed to SM. Founded in 2003 | ET | AVCODES |
| 9 | SM | St. Marys R.R. Co. | 1/1975; eliminated 1/1979; 1/1980-7/2000; eliminated 7/2004; 7/2005 | | NAKINA |
| 10 | SM | St. Marys R.R. Co. | 1/75; eliminated 1/79; 1/80-7/2000 | | NRHS |
| 11 | SM | ST. MARYS RAILROAD CO. | | | PWRC |
| 12 | SM | St. Mary's Railroad | | | RSRV |
| 13 | SM | SAINT MARYS RAILROAD COMPANY | | | SCAC4 |
| 14 | SM | St. Marys R.R. Co. | | USA | TRAFFIC |
| 15 | SM | Scandinavian Motortransport AB | | SE | VKM |
| 16 | SMA | SMA Airlines Nig. Limited | Callsign: Sesame, | WAN | AVCODES |
| 17 | SMA | SMA Airlines | | | ICAO1 |
| 18 | SMA | San Manuel Arizona R.R. Co. | 1/1975-7/2005 | | NAKINA |
| 19 | SMA | San Manuel Arizona R.R. Co. | 1/75-7/2000 | | NRHS |
| 20 | SMA | SAN MANUEL ARIZONA RAILROAD COMPANY | | | PWRC |
| 21 | SMA | San Manuel Arizona Railroad | | | RSRV |
| 22 | SMAA | SEA MASTER SHIPPING GMBH | | | SCAC4 |
| 23 | SMAB | SMALL, BLAKE F | | | SCAC4 |
| 24 | SMAC | STEELMASTE | | | SCAC4 |
| 25 | SMAE | SAM EXPRESS | | | SCAC4 |
| 26 | SMAG | STATE MARINE-ISTHMIAN AGENCY INC. | | | PWRC |
| 27 | SMAH | SMITH FARM SERVICE INC | | | SCAC4 |
| 28 | SMAL | SMITH, AL MOVING AND FURNITURE CO I | | | SCAC4 |
| 29 | SMAM | STREETER, MATT L TRUCKING | | | SCAC4 |
| 30 | SMAQ | S & M TRANSPORT INC | | | SCAC4 |
| 31 | SMAR | STERLING MARINE TRANSPORT LLC | | | SCAC4 |
| 32 | SMAR | South Maitland Railways | Real: SMR | AUS | TRAFFIC |
| 33 | SMART | SMART CORPORATION s.r.o. | | SK | VKM |
| 34 | SMARTC | Sonoma–Marin Area Rail Transit | Real: SMART | US-CA | TRAFFIC |
| 35 | SMARTD | Suburban Mobility Authority for Regional Transportation | Real: SMART, City: Detroit, Beginning operations in 1967 as the Southeastern Michigan Transportation Authority (SEMTA) in Wayne, Oakland and Macomb Counties. Its name was changed to SMART in 1989. | USA | TRAFFIC |
| 36 | SMAS | SOUND MOVING AND STORAGE (DIV OF JA | | | SCAC4 |
| 37 | SMAU | SMART CONTAINERS KAMIL BIESZK | | PL | BIC |
| 38 | SMAU | AUSIMONT S.P.A., MONTEDISON INTERMI | | | SCAC3 |
| 39 | SMAU | AUSIMONT S.P.A., MONTEDISON INTERMI | | | SCAC4 |
| 40 | SMAV | SUMMI | | | SCAC4 |
| 41 | SMAX | Siemens-Allis, Inc. | added 4/1985; eliminated 4/1986 | | NAKINA |
| 42 | SMAX | Siemens | added 4/1986; eliminated 10/1988 | | NAKINA |
| 43 | SMAX | Siemens-Allis, Inc. | added 4/85; eliminated 4/86 | | NRHS |
| 44 | SMAX | Siemens | added 4/86; eliminated 10/88 | | NRHS |
| 45 | SMAX | SIEMENS INC. [SIEMENS-ALLIS, INC.] | | | PWRC |
| 46 | SMB | Simba Air Cargo Ltd. | Callsign: Simbair, Ceased operations. | EAK | AVCODES |
| 47 | SMB | Solothurn - Moutier-Bahn | | CH | TRAFFIC |
| 48 | SMBC | SIMBEL E N E | | | SCAC4 |
| 49 | SMBF | SMITH, JOHN D TRUCKING LLC | | | SCAC4 |
| 50 | SMBI | SMB MFG INC | | | SCAC4 |
| 51 | SMBJ | SMS TRUCKING INC | | | SCAC4 |
| 52 | SMBK | SIMBECK INC | | | SCAC4 |
| 53 | SMBL | SMITH BROTHERS TRANSPORT LLC | | | SCAC4 |
| 54 | SMBN | SMITH TRUCKING INC | | | SCAC4 |
| 55 | SMBO | SMITH BROTHERS TRUCKING CO INC | | | SCAC4 |
| 56 | SMBP | SMOOT BROS TRANSPORTATION | | | SCAC4 |
| 57 | SMBQ | SPECIALITES MB INC | | | SCAC4 |
| 58 | SMBR | SMT TRUCKING COMPANY | | | SCAC4 |
| 59 | SMBT | SERRATOS MOBILE HOMES | | | SCAC4 |
| 60 | SMBU | SAMBU LINE, S.A. | | | SCAC4 |
| 61 | SMBV | SOUTHERN MAINE SITEWORK INC | | | SCAC4 |
| 62 | SMBW | SHARP, MICHAEL A TRUCKING | | | SCAC4 |
| 63 | SMBY | SUPERS | | | SCAC4 |
| 64 | SMC | Sabang Merauke Raya Air Charter PT. | Callsign: Samer, Name changed to SMAC (Sabang Merauke Raya Air Charter), PT. | RI | AVCODES |
| 65 | SMC | SMAC (Sabang Merauke Raya Air Charter), PT. | Callsign: Samer, Name changed from Sabang Merauke Raya Air Charter PT. | RI | AVCODES |
| 66 | SMC | Comlux San Marino S.r.l. | Callsign: Comlux, | RSM | AVCODES |
| 67 | SMC | Sabang Merauke Raya Air Charter | | | ICAO1 |
| 68 | SMC | A. E. STALEY MANUFACTURING CO. | | | PWRC |
| 69 | SMC | Chemin de Fer & Autobus Sierre-Montana-Crans | | CH | TRAFFIC |
| 70 | SMCD | SEAMATES CONSOLIDATION SERVICE INC | | | SCAC4 |
| 71 | SMCE | SKYLINE MAIL CARRIERS INC | | | SCAC4 |
| 72 | SMCF | SMITH CARTAGE INC | | | SCAC4 |
| 73 | SMCF | Sercice Militaire des Chemines de Fer | | FR | VKM |
| 74 | SMCI | SPECIAL MACHINING CO INC | | | SCAC4 |
| 75 | SMCJ | SUMMERFORD TRUCK LINE INC | | | SCAC4 |
| 76 | SMCL | SMITH, C. L., TRUCKING | | | SCAC1 |
| 77 | SMCN | SAMS TRUCKING | | | SCAC4 |
| 78 | SMCO | SAN MARCOS TRANSFER | | | SCAC4 |
| 79 | SMCO | S.M.Coaches | | GB | TRAFFIC |
| 80 | SMCP | SECO MANUFACTURING COMPANY INC | | | SCAC4 |
| 81 | SMCQ | SMITH, W., CARTAGE COMPANY, INC | | | SCAC1 |
| 82 | SMCQ | SMITH, W CARTAGE COMPANY INC | | | SCAC4 |
| 83 | SMCT | SMITH, C R TRUCKING | | | SCAC4 |
| 84 | SMCU | SM CONTAINER LINES | | ROK | BIC |
| 85 | SMCU | ASTRIUM GMBH | | | SCAC4 |
| 86 | SMCV | SAN MARCOS GROUP LLC | | | SCAC4 |
| 87 | SMCX | Staso Milling Co. | 7/1930-7/1932 | | NAKINA |
| 88 | SMCX | The Simmons Co. | 1/1943-1/1946 | | NAKINA |
| 89 | SMCX | The Altus Co. | added 1/1962; eliminated 1/1963 | | NAKINA |
| 90 | SMCX | Standard Milling Co. | added 1/1963; 7/1965-4/1970; eliminated 4/1972 | | NAKINA |
| 91 | SMCX | San Miguel Electric Cooperative, Inc. | added 10/1981; 1/1994-7/2005 | | NAKINA |
| 92 | SMCX | The Altus Co. | added 1/62 | | NRHS |
| 93 | SMCX | Standard Milling Co. | 7/65-4/70; eliminated 4/72 | | NRHS |
| 94 | SMCX | San Miguel Electric Cooperative, Inc. | added 10/81; 1/94-7/2000 | | NRHS |
| 95 | SMCX | *STASO MILLING CO. | | | PWRC |
| 96 | SMCX | *SIMMONS CO. | | | PWRC |
| 97 | SMCX | *STANDARD MILLING CO. [ALTUS CO.] | | | PWRC |
| 98 | SMCX | +SAN MIGUEL ELECTRIC COOPERATIVE, INC. | | | PWRC |
| 99 | SMCX | San Miguel Electric Cooperative | | | RSRV |
| 100 | SMCX | SAN MIGUEL ELECTRIC COOPERATIVE INC | | | SCAC4 |
