| 1 | ISG | Sixcargo S.p.A. | IATA: 6P, Callsign: Italcargo, Name changed to Clubair Sixgo S.p.A. | I | AVCODES |
| 2 | ISG | Clubair Sixgo S.p.A. | IATA: 6P, Callsign: Italcargo, Name changed from Sixcargo S.p.A. | I | AVCODES |
| 3 | ISG | Club Air | IATA: 6P | | ICAO1 |
| 4 | ISG | ISG RAILWAYS | | | PWRC |
| 5 | ISG | ISG Railways | | | RSRV |
| 6 | ISGE | ISG EXPRESS INC | | | SCAC4 |
| 7 | ISGI | INTERSTATE SERVICE GROUP INC | | | SCAC4 |
| 8 | ISGL | INTERMODAL SOLUTIONS GROUP LLC | | | SCAC4 |
| 9 | ISGT | ISG TRANSPORTATION INC | | | SCAC4 |
| 10 | ISGU | INCHCAPE SHIPPING SERVICE | | | SCAC4 |
| 11 | ISGX | International Steel Group d/b/a ISG Burns Harbor, Inc. | 7/2005 (not listed) | | NAKINA |
| 12 | ISGX | INTERNATIONAL STEEL GROUP d/b/a ISG BURNS HARBOR, INC. | | | PWRC |
| 13 | ISGX | INTERNATIONAL STEEL GROUP D/B/A ISG | | | SCAC4 |
