| 1 | SP | Solinair Latelsko Podjetjet d.o.o. | ICAO: SOP, Callsign: Solinair, IATA Prefix: 265, IATA designator changed to ZS. | SLO | AVCODES |
| 2 | SP | Sociedade Acoriana de Tranportes Aereos, Lda. (SATA) | Callsign: SAT, | P | AVCODES |
| 3 | SP | Southern Pacific Co. (Pacific Lines) | 1/1941-7/1965 | | NAKINA |
| 4 | SP | Southern Pacific Co. | 10/1966 | | NAKINA |
| 5 | SP | Southern Pacific Co. (Pacific Lines) | 4/1970 | | NAKINA |
| 6 | SP | Southern Pacific Transportation Co. | 1/1975-1/1994; eliminated 10/1998 | | NAKINA |
| 7 | SP | Union Pacific R.R. Co. | added 10/1998; 7/2000-7/2005 | | NAKINA |
| 8 | SP | Southern Pacific Co. (Pacific Lines) | 1/52-7/65 | | NRHS |
| 9 | SP | Southern Pacific Co. | Oct-66 | | NRHS |
| 10 | SP | Southern Pacific Co. (Pacific Lines) | Apr-70 | | NRHS |
| 11 | SP | Southern Pacific Transportation Co. | 1/75-1/94; eliminated 10/98 | | NRHS |
| 12 | SP | Union Pacific R.R. Co. | added 10/98; 7/2000 | | NRHS |
| 13 | SP | UNION PACIFIC RAILROAD [SOUTHERN PACIFIC TRANSP. CO.] | | | PWRC |
| 14 | SP | Southern Pacific Railroad (Union Pacific Railroad) | | | RSRV |
| 15 | SP | SOUTHERN PACIFIC TRANSPORTATION COM | | | SCAC4 |
| 16 | SP | Southern Pacific | Southern (New Southern Railway Ltd.) is the latest name of the train operating company that took over from Connex South Central on the routes to South London, Surrey, and Sussex from Victoria and London Bridge. The company was originally known as South Central, but on 30 May 2004, the franchise was rebranded as Southern, in a deliberate recollection of pre-nationalisation Southern Railway. Southern also operates the cross-London Watford Junction to Gatwick Airport / Brighton route via Kensington (Olympia) and Clapham Junction (the West London Line). The franchise is owned by Govia, a joint venture between transport groups Go-Ahead Group and Keolis. | USA | TRAFFIC |
| 17 | SP | Slovenská pošta, a.s. | | SK | VKM |
| 18 | SP&S | Spokane, Portland & Seattle Ry. Co. | 7/1923-4/1938 | | NAKINA |
| 19 | SP&S | Spokane, Portland & Seattle Ry. Co. | Apr-38 | | NRHS |
| 20 | SP&S | SPOKANE, PORTLAND & SEATTLE RWY. CO. | | | PWRC |
| 21 | SPA | Sierra Pacific Airlines, Inc. | IATA: SI, Callsign: Sierra Pacific, Designator SI* reinstated by IATA | USA | AVCODES |
| 22 | SPA | Sierra Pacific Airlines | | | ICAO1 |
| 23 | SPA | SIERRA PACIFIC TOURS | | | PWRC |
| 24 | SPA | SIERRA PACIFIC TOURS | | | SCAC4 |
| 25 | SPA | Spanish Army | | E | TRAFFIC |
| 26 | SPAA | SERNA PEREZ, ADAN | | | SCAC4 |
| 27 | SPAB | SPORTS ASSOCIATED INC | | | SCAC4 |
| 28 | SPAC | SPACE AGE FUEL INC | | | SCAC4 |
| 29 | SPAD | SUPREME ADVANTAGE | | | SCAC4 |
| 30 | SPAD | Szczecińskie Przedsiębiorstwo Autobusowe Dąbie | | PL | TRAFFIC |
| 31 | SPAE | SPRING CREEK HB INC | | | SCAC4 |
| 32 | SPAF | SPARKLING SNOW INC | | | SCAC4 |
| 33 | SPAG | SPRINGLAND MANUFACTURING | | | SCAC4 |
| 34 | SPAG | SPITZKE AG | | DE | VKM |
| 35 | SPAH | SPARROW SHIPPING LLC | | | SCAC4 |
| 36 | SPAI | SPAIN'S TRANSFER, INC | | | SCAC1 |
| 37 | SPAI | SPAINS TRANSFER INC | | | SCAC4 |
| 38 | SPAK | Szczecińskie Przedsiębiorstwo Autobusowe Klonowica | | PL | TRAFFIC |
| 39 | SPANG | Omnibus-Unternehmen Johann Spangler | In the AVV: Augsburger Verkehrs- und Tarifverbund | D | TRAFFIC |
| 40 | SPANT | Spangler Touristik | | D | TRAFFIC |
| 41 | SPAP | SIMPLICITY AIR LTD | | | SCAC4 |
| 42 | SPAS | SANDA PASTRIES INC | | | SCAC4 |
| 43 | SPAX | Shreveport Producing & Refining Corp. | 7/1923 | | NAKINA |
| 44 | SPAX | Shreveport-El Dorado Pipe Line Co., Inc. | 7/1930 | | NAKINA |
| 45 | SPAX | Spartan Refining Co., Inc. | 7/1932-7/1935 | | NAKINA |
| 46 | SPAX | Atlas Pipe Line Corp. | 7/1937-4/1938 | | NAKINA |
| 47 | SPAX | Southeastern Pennsylvania Transportation Authority | added 10/1984; eliminated 4/1990; 1/1994-7/2005 (not listed) | | NAKINA |
| 48 | SPAX | Atlas Pipeline Corp. | Apr-38 | | NRHS |
| 49 | SPAX | Southeastern Pennsylvania Transportation Authority | added 10/84; eliminated 4/90; 1/94-7/2000 | | NRHS |
| 50 | SPAX | *ATLAS PIPE LINE CO. [SPARTAN REFINING CO., INC.; SHREVEPORT-EL DORADO PIPE LINE CO.; SHREVEPORT PRODUCING & REFINING CORP.] | | | PWRC |
| 51 | SPAX | +SOUTHEASTERN PENNSYLVANIA TRANSPORTATION AUTHORITY (SEPTA) | | | PWRC |
| 52 | SPAX | Southeastern Pennsylvania Transportation Authority (SEPTA) | | | RSRV |
| 53 | SPAX | SOUTHEASTERN PENNSYLVANIA TRANSPORT | | | SCAC4 |
| 54 | SPAZ | SPANISH LINES | | | PWRC |
| 55 | SPAZ | Spanish Lines | | | RSRV |
| 56 | SPAZ | SPANISH LINES | | | SCAC4 |
| 57 | SPB | Springbok Classic Air | Callsign: Spring Classic, | ZA | AVCODES |
| 58 | SPB | Springbok Classic Air | | | ICAO1 |
| 59 | SPB | St. Paul Bridge & Terminal Ry. Co. | 8/1920-7/1932 | | NAKINA |
| 60 | SPB | *ST. PAUL BRIDGE & TERMINAL RWY. CO. | | | PWRC |
| 61 | SPB | *SUPER SERVICE BUS COMPANY | | | PWRC |
| 62 | SPB | Schynige Platte Bahn | | CH | TRAFFIC |
| 63 | SPBB | Starostwo Powiatowe w Bielsku-Bialej | | PL | TRAFFIC |
| 64 | SPBE | SANCHEZ PICO, EUGENIO | | | SCAC4 |
| 65 | SPBF | SUPERB TRANSPORT | | | SCAC4 |
| 66 | SPBG | SPACE TRUCK USA CORP | | | SCAC4 |
| 67 | SPBH | SAHLEN PACKING COMPANY INC | | | SCAC4 |
| 68 | SPBK | SHARKWA | | | SCAC4 |
| 69 | SPBN | SILOS PLUS TRANSFER LLC | | | SCAC4 |
| 70 | SPBO | SMITH PROVISION CO INC | | | SCAC4 |
| 71 | SPBP | SPECIALIZED CARRIER COMPANY INC | | | SCAC4 |
| 72 | SPBR | STOCKTON PUBLIC BELT RAILROAD | | | PWRC |
| 73 | SPBW | STONE CONSTRUCTION EQPT INC | | | SCAC4 |
| 74 | SPC | Skyworld Airlines | Callsign: Port, | USA | AVCODES |
| 75 | SPC | Skyworld Airlines | | | ICAO1 |
| 76 | SPC | SOUTHERN PACIFIC [SOUTH PACIFIC COAST RAILROAD] | | | PWRC |
| 77 | SPC | SPIRIT COACH LLC | | | SCAC4 |
| 78 | SPCA | SOPRO CARRIERS INC | | | SCAC4 |
| 79 | SPCC | SOUTHWESTERN PORTLAND CEMENT CO. | | | PWRC |
| 80 | SPCC | STAPLES OIL CO INC | | | SCAC4 |
| 81 | SPCC | Southern Peru Copper Corporation | | PE | TRAFFIC |
| 82 | SPCD | SPRINT COURIER INC | | | SCAC4 |
| 83 | SPCF | SPECIFIED FITTINGS INC | | | SCAC4 |
| 84 | SPCG | SPECIALIZED TRANSPORTATION INC | | | SCAC4 |
| 85 | SPCH | Quest Communications Corp. | 7/2000-7/2005 | | NAKINA |
| 86 | SPCH | Quest Communications Corp. | Jul-00 | | NRHS |
| 87 | SPCH | QUEST COMMUNICATIONS CORP. | | | PWRC |
| 88 | SPCH | Quest Communications Corporation | | | RSRV |
| 89 | SPCH | SUPREME CHAIN LOGISTICS LTD | | | SCAC4 |
| 90 | SPCH | Spolek pro chemickou a hutní výrobu, akciová společnost | | CZ | VKM |
| 91 | SPCI | SPECIAL COMMODITIES INC | | | SCAC4 |
| 92 | SPCJ | SPECIAL DISTRIBUTION CALIFORNIA LLC | | | SCAC4 |
| 93 | SPCL | SPECIALIZED TRANSPORT SERVICE | | | SCAC4 |
| 94 | SPCM | SPENCER COMPANIES INCORPORATED | | | SCAC4 |
| 95 | SPCN | SEPSA CUSTODIA DE VALORES SA DE CV | | | SCAC4 |
| 96 | SPCO | SHOPCAM INC | | | SCAC4 |
| 97 | SPCR | SUPERIOR CARRIERS INC | | | SCAC4 |
| 98 | SPCT | SPENCER TRANSPORTATION | | | SCAC4 |
| 99 | SPCU | PACIFIC CONTAINER LEASE PTY LIMITED | | | PWRC |
| 100 | SPCU | Spacific Container Lease Pty | | | RSRV |
