| 4701 | SHXN | SHORTLINE AG INC | | | SCAC4 |
| 4702 | SHXO | SHARCO EXPRESS | | | SCAC4 |
| 4703 | SHXP | SHIPPERS TRANSPORT SERVICES LLC | | | SCAC4 |
| 4704 | SHXR | SOUTH TEXAS OIL RIG SERVICES LLC | | | SCAC4 |
| 4705 | SHXT | SCORPIO HANDYMAX TANKER POOL LTD | | | SCAC4 |
| 4706 | SHXV | SHOOTING STAR TRANSPORT INC | | | SCAC4 |
| 4707 | SHXW | S & H TRANSPORT LLC | | | SCAC4 |
| 4708 | SHY | Sik-Ay Hava Tasimacilik A.S. | Callsign: Antalya Bird, ICAO callsign changed to Sky Power | TR | AVCODES |
| 4709 | SHY | Sik-Ay Hava Tasimacilik A.S. | IATA: ZY, Callsign: Sky Power, Filed for bankruptcy and ceased all flight operations on 04 June 2013. ICAO callsign changed from Antalya Bird | TR | AVCODES |
| 4710 | SHY | Sky Airlines | | | ICAO1 |
| 4711 | SHYC | SCHUYLER COOPERATIVE ASSN | | | SCAC4 |
| 4712 | SHYD | SHINYO DREAM LIMITED | | | SCAC4 |
| 4713 | SHYF | SMITH FAMILY FARM | | | SCAC4 |
| 4714 | SHYG | STANDLEE HAY TRUCKING CO INC | | | SCAC4 |
| 4715 | SHYH | S & T HEAVY HAUL LP | | | SCAC4 |
| 4716 | SHYI | STH LOGISTICS INC | | | SCAC4 |
| 4717 | SHYK | SEASHORE TROLLEY MUSEUM | | | SCAC4 |
| 4718 | SHYN | SAMPSON, HECTOR YOVANY | | | SCAC4 |
| 4719 | SHYQ | SRIVITHYA INC | | | SCAC4 |
| 4720 | SHYS | SHELTER SYSTEMS LIMITED | | | SCAC4 |
| 4721 | SHYT | SHAY TRUCKING LLC | | | SCAC4 |
| 4722 | SHYV | SCOTT SHUTTLE SERVICES | | | SCAC4 |
| 4723 | SHYY | SHOTEN, SHIMAYA LIMITED | | | SCAC4 |
| 4724 | SHZ | Scotia Helicopter Services Ltd. | Callsign: Rotabird, | GB | AVCODES |
| 4725 | SHZB | SUN HORIZON SPECIALIZED LLC | | | SCAC4 |
| 4726 | SHZC | SANCHEZ | | | SCAC4 |
| 4727 | SHZF | SCC HAAS TRUCKING INC | | | SCAC4 |
| 4728 | SHZG | SCHMITT TRUCKING | | | SCAC4 |
| 4729 | SHZI | SOUTHERN RESIN INC | | | SCAC4 |
| 4730 | SHZP | SHIPTRANSPORTAL | | | SCAC4 |
| 4731 | SHZS | SEAHORSE SHIPPING CORPORATION | | | SCAC4 |
| 4732 | SHZV | SHOWTIME STALL RENTALS | | | SCAC4 |
| 4733 | SHZY | SUNSHINE HEAVY HAULING INC | | | SCAC4 |
| 4734 | SI | Skynet Airlines Limited | ICAO: SIH, Callsign: Bluejet, IATA designator changed to SI | IRL | AVCODES |
| 4735 | SI | Friesenflug GmbH & Co. KG | | D | AVCODES |
| 4736 | SI | Sierra Pacific Airlines, Inc. | ICAO: SPA, Callsign: Sierra Pacific, Designator SI* reinstated by IATA | USA | AVCODES |
| 4737 | SI | SaBer Air Private Limited | | SGP | AVCODES |
| 4738 | SI | Skynet Airlines Limited | ICAO: SIH, Callsign: Bluejet, founded in 2001. Ceased operations in 2004. IATA designator changed from SI* | IRL | AVCODES |
| 4739 | SI | Arab Wings Company | ICAO: AWS, Callsign: Arab Wings, Designator SI recalled by IATA | JOR | AVCODES |
| 4740 | SI | Airx Limited t/a Blue Islands | ICAO: BCI, Callsign: Blue Island, Name changed from Airx Limited t/a Lecocqs.com and then from Airx Limited t/a Rockhopper. IATA designator changed from AX*. ICAO designator changed from XAX | GBJ | AVCODES |
| 4741 | SI | Blue Islands Limited | ICAO: BCI, Callsign: Blue Island, Name changed from Airx Limited t/a Lecocqs.com and then from Airx Limited t/a Rockhopper. IATA designator changed from AX*. ICAO designator changed from XAX | GBJ | AVCODES |
| 4742 | SI | Spokane International R.R. Co. | 1/1975-1/1980; added 1/1988 | | NAKINA |
| 4743 | SI | Union Pacific R.R. Co. | added 4/1988; 1/1994; eliminated 4/1994; 7/2000-7/2005 | | NAKINA |
| 4744 | SI | Spokane International R.R. Co. | 1/75-1/80; added 1/88 | | NRHS |
| 4745 | SI | Union Pacific R.R. Co. | added 4/88; 1/94; eliminated 4/94; 7/2000 | | NRHS |
| 4746 | SI | UNION PACIFIC RAILROAD CO. [SPOKANE INTERNATIONAL RR] | | | PWRC |
| 4747 | SI | Spokane International Railroad (Union Pacific Railroad) | | | RSRV |
| 4748 | SI | Spokane International R.R. Co. | | USA | TRAFFIC |
| 4749 | SI | Sistemi Territoriali S.p.a. | | IT | VKM |
| 4750 | SI&P | Southern Illinois Ry. and Power Co. | 7/1923-7/1930 | | NAKINA |
| 4751 | SI&P | Southern Illinois Ry. & Power Co. | 7/1932 | | NAKINA |
| 4752 | SI&P | SOUTHERN ILLINOIS RWY. & POWER CO. | | | PWRC |
| 4753 | SIA | Singapore Airlines | IATA: SQ, Callsign: Singapore, IATA Prefix: 618, Name changed to Singapore Airlines Limited | SGP | AVCODES |
| 4754 | SIA | Singapore Airlines Limited | IATA: SQ, Callsign: Singapore, IATA Prefix: 618, Name changed from Singapore Airlines | SGP | AVCODES |
| 4755 | SIA | Singapore Airlines | IATA: SQ | | ICAO1 |
| 4756 | SIA | Singapore Airlines Limited | | SGP | TRAFFIC |
| 4757 | SIAA | SIERRAS ALCARAZ, ALEJANDRO | | | SCAC4 |
| 4758 | SIAD | SANTSAR INDUSTRIES INC | | | SCAC4 |
| 4759 | SIAG | SATILLA TRANSPORT INC | | | SCAC4 |
| 4760 | SIAL | SIMMONS, L TRUCKING LLC | | | SCAC4 |
| 4761 | SIAM | SCHNEIDERS IRON & METAL INC | | | SCAC4 |
| 4762 | SIAN | SIARC INC | | | SCAC4 |
| 4763 | SIAP | SILVERTRANS INC | | | SCAC4 |
| 4764 | SIAR | SIMBA LOGISTICS LTD | | | SCAC4 |
| 4765 | SIAT | SST INTERNATIONAL INC | | | SCAC4 |
| 4766 | SIAU | SIAD SOCIETA ITALIANA ACETILENE & DERIVATI SPA | | I | BIC |
| 4767 | SIAU | SIAD SOCIETA ITALIANA ACETILENE & D | | | SCAC4 |
| 4768 | SIAV | SIMPSON ENTERPRISES LTD | | | SCAC4 |
| 4769 | SIAW | SILVER ARROW, INC | | | SCAC1 |
| 4770 | SIAW | SILVER ARROW INC | | | SCAC4 |
| 4771 | SIAY | SOLIDARITE 2000 INC | | | SCAC4 |
| 4772 | SIB | Joint Stock Company SIAT (Sibaviatrans) | IATA: 5M, Callsign: Sibavia, IATA Prefix: 842, Suspended operations at the end of September 2008 due to the Air Union collapse. | RUS | AVCODES |
| 4773 | SIB | Siba S.p.A. | | I | AVCODES |
| 4774 | SIB | Sea Air Ltd. | Callsign: Sea Air, | SLO | AVCODES |
| 4775 | SIB | Sibaviatrans | IATA: 5M | | ICAO1 |
| 4776 | SIBB | SOUTHWESTERN ILLINOIS BUS COMPANY L | | | SCAC4 |
| 4777 | SIBD | SIMON TRANSPORT LLC (BROKERAGE DIVI | | | SCAC4 |
| 4778 | SIBG | SIT | | | SCAC4 |
| 4779 | SIBI | SISBRO, INC | | | SCAC1 |
| 4780 | SIBI | SISBRO INC | | | SCAC4 |
| 4781 | SIBIU | Sibiu: Tursib | | RO | TRAFFIC |
| 4782 | SIBN | SIBRIAN TRUCKING | | | SCAC4 |
| 4783 | SIBP | SIMBA TRANSPORT LTD | | | SCAC4 |
| 4784 | SIBQ | SERVICES INTERNATIONAL | | | SCAC4 |
| 4785 | SIBS | SIMPSON FISHING CO LTD | | | SCAC4 |
| 4786 | SIBT | SIBLEY TRUCKING INC | | | SCAC4 |
| 4787 | SIBU | GE SIMONS INTERNATIONAL TRANSPORT BV | | NL | BIC |
| 4788 | SIBU | GE SIMONS INTERNATIONAL TRANSPORT B | | | SCAC4 |
| 4789 | SIBV | SCHILLI DISTRIBUTION SERVICES INC | | | SCAC4 |
| 4790 | SIBZD | Siberian Railway | | RUS | TRAFFIC |
| 4791 | SIC | Air Sicilia S.p.A. | IATA: BM, Callsign: Air Sicilia, Ceased operations during 2004. Name changed from Air Sicilia S.R.L. | I | AVCODES |
| 4792 | SIC | Air Sicilia S.R.L. | IATA: BM, Callsign: Air Sicilia, Name changed to Air Sicilia S.p.A. | I | AVCODES |
| 4793 | SICC | SIX ZERO THREE SIX SIX FIVE ONE (60 | | | SCAC4 |
| 4794 | SICD | SPECTRAN, INC | | | SCAC1 |
| 4795 | SICF | SLOAN IMPLEMENT COMPANY | | | SCAC4 |
| 4796 | SICG | SICKLER'S TRUCKING | | | SCAC4 |
| 4797 | SICH | STORM INTERSTATE CO | | | SCAC4 |
| 4798 | SICJ | SILVER CITY ALUMINUM CORP | | | SCAC4 |
| 4799 | SICL | SILVER CITY LUMBER INC | | | SCAC4 |
| 4800 | SICO | SIMPSON EXPRESS AND TRANSFER INC | | | SCAC4 |
