| 1 | SPA | Sierra Pacific Airlines, Inc. | IATA: SI, Callsign: Sierra Pacific, Designator SI* reinstated by IATA | USA | AVCODES |
| 2 | SPA | Sierra Pacific Airlines | | | ICAO1 |
| 3 | SPA | SIERRA PACIFIC TOURS | | | PWRC |
| 4 | SPA | SIERRA PACIFIC TOURS | | | SCAC4 |
| 5 | SPA | Spanish Army | | E | TRAFFIC |
| 6 | SPAA | SERNA PEREZ, ADAN | | | SCAC4 |
| 7 | SPAB | SPORTS ASSOCIATED INC | | | SCAC4 |
| 8 | SPAC | SPACE AGE FUEL INC | | | SCAC4 |
| 9 | SPAD | SUPREME ADVANTAGE | | | SCAC4 |
| 10 | SPAD | Szczecińskie Przedsiębiorstwo Autobusowe Dąbie | | PL | TRAFFIC |
| 11 | SPAE | SPRING CREEK HB INC | | | SCAC4 |
| 12 | SPAF | SPARKLING SNOW INC | | | SCAC4 |
| 13 | SPAG | SPRINGLAND MANUFACTURING | | | SCAC4 |
| 14 | SPAG | SPITZKE AG | | DE | VKM |
| 15 | SPAH | SPARROW SHIPPING LLC | | | SCAC4 |
| 16 | SPAI | SPAIN'S TRANSFER, INC | | | SCAC1 |
| 17 | SPAI | SPAINS TRANSFER INC | | | SCAC4 |
| 18 | SPAK | Szczecińskie Przedsiębiorstwo Autobusowe Klonowica | | PL | TRAFFIC |
| 19 | SPANG | Omnibus-Unternehmen Johann Spangler | In the AVV: Augsburger Verkehrs- und Tarifverbund | D | TRAFFIC |
| 20 | SPANT | Spangler Touristik | | D | TRAFFIC |
| 21 | SPAP | SIMPLICITY AIR LTD | | | SCAC4 |
| 22 | SPAS | SANDA PASTRIES INC | | | SCAC4 |
| 23 | SPAX | Shreveport Producing & Refining Corp. | 7/1923 | | NAKINA |
| 24 | SPAX | Shreveport-El Dorado Pipe Line Co., Inc. | 7/1930 | | NAKINA |
| 25 | SPAX | Spartan Refining Co., Inc. | 7/1932-7/1935 | | NAKINA |
| 26 | SPAX | Atlas Pipe Line Corp. | 7/1937-4/1938 | | NAKINA |
| 27 | SPAX | Southeastern Pennsylvania Transportation Authority | added 10/1984; eliminated 4/1990; 1/1994-7/2005 (not listed) | | NAKINA |
| 28 | SPAX | Atlas Pipeline Corp. | Apr-38 | | NRHS |
| 29 | SPAX | Southeastern Pennsylvania Transportation Authority | added 10/84; eliminated 4/90; 1/94-7/2000 | | NRHS |
| 30 | SPAX | *ATLAS PIPE LINE CO. [SPARTAN REFINING CO., INC.; SHREVEPORT-EL DORADO PIPE LINE CO.; SHREVEPORT PRODUCING & REFINING CORP.] | | | PWRC |
| 31 | SPAX | +SOUTHEASTERN PENNSYLVANIA TRANSPORTATION AUTHORITY (SEPTA) | | | PWRC |
| 32 | SPAX | Southeastern Pennsylvania Transportation Authority (SEPTA) | | | RSRV |
| 33 | SPAX | SOUTHEASTERN PENNSYLVANIA TRANSPORT | | | SCAC4 |
| 34 | SPAZ | SPANISH LINES | | | PWRC |
| 35 | SPAZ | Spanish Lines | | | RSRV |
| 36 | SPAZ | SPANISH LINES | | | SCAC4 |