| 1 | SKO | Scottish Airways Flyers Ltd. | Callsign: Skywork, | GB | AVCODES |
| 2 | SKO | Scottish Airways Flyers | | | ICAO1 |
| 3 | SKODA | | | CZ | TRAFFIC |
| 4 | SKOG | S S SKIKOS TRUCKING INC | | | SCAC4 |
| 5 | SKOI | STARK OIL | | | SCAC4 |
| 6 | SKOJ | SHOOKS OIL BURNER SERVICE & FUEL OI | | | SCAC4 |
| 7 | SKOL | South Kansas & Oklahoma R.R., Inc. | added 4/1992; 1/1994; eliminated 1/1997; added 7/1998; 7/2000; eliminated 1/2005; added 4/2005; 7/2005 | | NAKINA |
| 8 | SKOL | South Kansas & Oklahoma R.R., Inc. | added 4/92; 1/94; eliminated 1/97; added 7/98; 7/2000 | | NRHS |
| 9 | SKOL | SOUTH KANSAS & OKLAHOMA RAILROAD, INC. | | | PWRC |
| 10 | SKOL | South Kansas and Oklahoma Railroad | | | RSRV |
| 11 | SKOL | SOUTH KANSAS & OKLAHOMA RAILROAD IN | | | SCAC4 |
| 12 | SKOL | South Kansas & Oklahoma R.R., Inc. | | USA | TRAFFIC |
| 13 | SKOM | SASHIKO MARITIME S A | | | SCAC4 |
| 14 | SKON | SKELTON TRUCK LINES LTD | | | SCAC4 |
| 15 | SKOR | SITKO, JOHN TRUCKING INC | | | SCAC4 |
| 16 | SKOTR | ŠKODA AUTO a.s. | | CZ | VKM |
| 17 | SKOV | SAMKOV TRANSPORT INC | | | SCAC4 |
| 18 | SKOY | SOUTHWEST KANSAS COOP SERVICE CO LL | | | SCAC4 |
