| 1 | SIQ | National Center for Atmospheric Research | Callsign: Science Quest, Name changed to Atmospheric Research Boulder. | USA | AVCODES |
| 2 | SIQ | Simon Air | IATA: 8U, Callsign: Simon, Designator 8U recalled by IATA | LB | AVCODES |
| 3 | SIQ | Atmospheric Research Boulder | Callsign: Science Quest, Name changed from National Center for Atmospheric Research. | USA | AVCODES |
| 4 | SIQA | SINO AMERICAN LINE | | | SCAC4 |
| 5 | SIQG | SINGLE SOURCE LOGISTICS INC | | | SCAC4 |
| 6 | SIQM | SEAPORT INTERMODAL | | | SCAC4 |
| 7 | SIQN | SONEIL INTERNATIONAL LIMITED | | | SCAC4 |
