| 5801 | SKRJ | Silkeborg - Kjellerup - Rødkærsbro Jernbane (Kjellerupbanen) | 1924 - 1968 | DK | jernbanen.dk |
| 5802 | SKRJ | SILK ROAD SOUTH | | | SCAC4 |
| 5803 | SKRJ | Silkeborg - Kjellerup - Rødkærsbro Jernbane (Kjellerupbanen) | | DK | TRAFFIC |
| 5804 | SKRL | S & K TRUCKING LTD | | | SCAC4 |
| 5805 | SKRM | S K R MOVING INC | | | SCAC4 |
| 5806 | SKRO | SILK ROAD TRANSPORT INC | | | SCAC4 |
| 5807 | SKRR | SNEAD, K R TRUCKING INC | | | SCAC4 |
| 5808 | SKRS | SKEETER TRUCKING | | | SCAC4 |
| 5809 | SKRU | SINOKOR MERCHANT MARINE CORP | | ROK | BIC |
| 5810 | SKRU | SINOKOR MERCHANT MARINE CO LTD | | | SCAC4 |
| 5811 | SKRW | SKUROW BROTHERS OIL COMPANY | | | SCAC4 |
| 5812 | SKRX | Skinner Refrigerator Lines | 8/1920 | | NAKINA |
| 5813 | SKRX | Schuylkill Railcar L.P. | added 10/1998; eliminated 7/2000; 7/2000-7/2005 (not listed) | | NAKINA |
| 5814 | SKRX | Schuylkill Railcar L.P. | added 10/98; 7/2000; eliminated 7/2000 | | NRHS |
| 5815 | SKRX | *SKINNER REFRIGERATOR LINES | | | PWRC |
| 5816 | SKRX | +SCHUYLKILL RAILCAR L.P. | | | PWRC |
| 5817 | SKRX | Schuylkill Railcar | | | RSRV |
| 5818 | SKRX | SCHUYLKILL RAILCAR LP | | | SCAC4 |
| 5819 | SKRZ | (XTRZ) XTRA INTERMODAL | | | PWRC |
| 5820 | SKRZ | XTRA Intermodal | | | RSRV |
| 5821 | SKRZ | XTRA INTERMODAL | | | SCAC4 |
| 5822 | SKS | Sky Service | Callsign: Sky Service, Name changed to abelog | B | AVCODES |
| 5823 | SKS | abelog | Ceased operations. Name changed from Sky Service | B | AVCODES |
| 5824 | SKS | Sky Link Aviation Services | | PK | AVCODES |
| 5825 | SKS | Sky Service | | | ICAO1 |
| 5826 | SKS | SKS Krnov, a.s. | | CZ | VKM |
| 5827 | SKSA | S K S CORPORATION | | | SCAC4 |
| 5828 | SKSB | SKS OBO LTD | | | SCAC4 |
| 5829 | SKSC | SANKO STEAMSHIP CO LTD | | | SCAC4 |
| 5830 | SKSD | STOKES SEEDS INC | | | SCAC4 |
| 5831 | SKSF | STRICKLAND, SHARON FRANCES | | | SCAC4 |
| 5832 | SKSG | SAMOTHRAKI SHIPPING CORP MONROVIA | | | SCAC4 |
| 5833 | SKSH | SK SHIPPING EUROPE | | | SCAC4 |
| 5834 | SKSI | SHARK SHIPPING LTD | | | SCAC4 |
| 5835 | SKSJ | SKS TRANSPORT INC | | | SCAC4 |
| 5836 | SKSK | SIMONS, KEN & SONS TRUCKING LLC | | | SCAC4 |
| 5837 | SKSM | SK SHIPPING CO LTD | | | SCAC4 |
| 5838 | SKSO | STICKS AND STONES MANUFACTURING INC | | | SCAC4 |
| 5839 | SKSP | SKAARUP SHIPPING CORPORATION | | | SCAC4 |
| 5840 | SKSQ | SKS INC | | | SCAC4 |
| 5841 | SKSR | SHIKES TRANSPORT (1992) LTD | | | SCAC4 |
| 5842 | SKSS | SKS TANKERS LTD | | | SCAC4 |
| 5843 | SKSU | SK SHIPPING LINE LLC | | UAE | BIC |
| 5844 | SKSV | SK TRANSPORTATION INC | | | SCAC4 |
| 5845 | SKT | Sky Services Aviation, S.L. | Callsign: Star-Jet, | E | AVCODES |
| 5846 | SKT | Aero Skytropic, S.A. | Callsign: Skytropic, | PA | AVCODES |
| 5847 | SKT | Skystar Airways | | | ICAO1 |
| 5848 | SKT | AB SkandiaTransport | | SE | VKM |
| 5849 | SKTA | SKOTIDAKIS GOAT FARM | | | SCAC4 |
| 5850 | SKTD | SUNTECK TRANSPORTATION INC | | | SCAC4 |
| 5851 | SKTF | SUPREME TANK INC | | | SCAC4 |
| 5852 | SKTG | ENTERPRISES INC OF STEVENVILLE | | | SCAC3 |
| 5853 | SKTG | ENTERPRISES INC OF STEVENVILLE | | | SCAC4 |
| 5854 | SKTH | SUPERIOR TANK & TRAILER CO INC, THE | | | SCAC4 |
| 5855 | SKTI | SKY TRUCKING CO | | | SCAC1 |
| 5856 | SKTI | SKY TRUCKING CO | | | SCAC4 |
| 5857 | SKTJ | STARSTRUCK TRANSPORTATION | | | SCAC4 |
| 5858 | SKTK | SACKETT TRUCKING | | | SCAC4 |
| 5859 | SKTL | S & K TRANSPORT LLC | | | SCAC4 |
| 5860 | SKTM | SHPEK TRANSPORT CORP | | | SCAC4 |
| 5861 | SKTQ | S & K TRUCKING LLC | | | SCAC4 |
| 5862 | SKTR | SHACKLETON TRANSPORTATION INC | | | SCAC4 |
| 5863 | SKTS | STOCK TRANSPORT INC | | | SCAC4 |
| 5864 | SKTT | SHARK TRANS INC | | | SCAC4 |
| 5865 | SKTW | SNIKTAW EXPRESS | | | SCAC4 |
| 5866 | SKTX | Ansco Investment Co. d/b/a Ski Train | 7/2005 (not listed) | | NAKINA |
| 5867 | SKTX | ANSCO INVESTMENT CO. d/b/a SKI TRAIN | | | PWRC |
| 5868 | SKTX | Ski Train | | | RSRV |
| 5869 | SKTX | ANSCO INVESTMENT COMPANY D/B/A SKI | | | SCAC4 |
| 5870 | SKTX | Ansco Investment Co. Ski Train | | USA | TRAFFIC |
| 5871 | SKTY | SIROKI TRANSPORT | | | SCAC4 |
| 5872 | SKU | Sky Service S.A. | IATA: H2, Callsign: Aerosky, IATA Prefix: 605, Name changed to Sky Service S.A. d/b/a Sky Airlines | RCH | AVCODES |
| 5873 | SKU | SK Air a.s. | IATA: S9, Callsign: Eska, | SK | AVCODES |
| 5874 | SKU | SK Air a.s. | Callsign: Eska, | SK | AVCODES |
| 5875 | SKU | Sky Service S.A. d/b/a Sky Airline | IATA: H2, Callsign: Aerosky, IATA Prefix: 605, Name changed to Sky Airline S.A. previously changed from Sky Service S.A. | RCH | AVCODES |
| 5876 | SKU | Sky Airline S.A. | IATA: H2, Callsign: Aerosky, IATA Prefix: 605, Name changed from Sky Service S.A. d/b/a Sky Airlines | RCH | AVCODES |
| 5877 | SKU | Sky Airline | IATA: H2 | | ICAO1 |
| 5878 | SKUA | SKUA SHIPPING LLC | | | SCAC4 |
| 5879 | SKUC | S & K TRUCKING | | | SCAC4 |
| 5880 | SKUL | STOKES TRUCKING INC | | | SCAC4 |
| 5881 | SKUO | STATKUS TRANSPORTATION CORP | | | SCAC4 |
| 5882 | SKUS | SKYLINK USA | | | SCAC4 |
| 5883 | SKV | Skyline NEPC Ltd. | IATA: D2, Callsign: Skyflyer, Designator D2 recalled by IATA | IND | AVCODES |
| 5884 | SKV | Sky Regional Airlines, Inc. | IATA: RS, Callsign: Sky Regional, IATA Designator changed to KV. | CDN | AVCODES |
| 5885 | SKV | Sky Regional Airlines, Inc. | IATA: KV, Callsign: Sky Regional, Ceased operations on 31 March 2021. IATA Designator changed from RS*. | CDN | AVCODES |
| 5886 | SKV | Skyside GmbH | Callsign: Sky Side, | A | AVCODES |
| 5887 | SKVA | SACKVILLE AUTO & RV LTD | | | SCAC4 |
| 5888 | SKVC | SMALL TRUCKING CORP | | | SCAC4 |
| 5889 | SKVD | SDVD | | | SCAC4 |
| 5890 | SKVI | SHAFER TRUCKING SERVICES INC | | | SCAC4 |
| 5891 | SKVQ | STARK SERVICE INC | | | SCAC4 |
| 5892 | SKVT | SAMKOV TRANS INC | | | SCAC4 |
| 5893 | SKW | SkyWest Airlines | IATA: OO, Callsign: Skywest, IATA Prefix: 302, Name changed from Sky West Airlines | USA | AVCODES |
| 5894 | SKW | Sky West Airlines | IATA: OO, Callsign: Skywest, IATA Prefix: 302, Name changed to SkyWest Airlines | USA | AVCODES |
| 5895 | SKW | SkyWest | IATA: OO | | ICAO1 |
| 5896 | SKW | SKW Piesteritz | | D | TRAFFIC |
| 5897 | SKWA | SKYWAY TRUCKING | | | SCAC4 |
| 5898 | SKWC | SKYWEST TRUCKING LTD | | | SCAC4 |
| 5899 | SKWE | SEKO WORLDWIDE | | | SCAC4 |
| 5900 | SKWL | SKYWAY LAWN EQUIPMENT LIMITED | | | SCAC4 |
