| 1 | KWY | SiFly Compagnia Aerea | IATA: 8X, Callsign: Sifly, IATA designator changed to S6 | I | AVCODES |
| 2 | KWY | SiFly Compagnia Aerea | IATA: S6, Callsign: Sifly, Designator S6 recalled by IATA | I | AVCODES |
| 3 | KWY | SiFly Compagnia Aerea | IATA: S6, Callsign: Sifly, Ceased operations on 06 October 2001. Designator S6 reinstated by IATA | I | AVCODES |
| 4 | KWY | Key Air International | Callsign: Keyair, Commenced operations December 1968 (as Thunderbird Airlines). Filed for Chapter 11 bankruptcy protection in 1993. Ceased operations May 1993. | USA | AVCODES |
| 5 | KWYL | KEY WAY LLC | | | SCAC4 |
| 6 | KWYQ | KWIK-WAY DELIVERY | | | SCAC3 |
| 7 | KWYT | KINGWAY TRANSIT CO LTD | | | SCAC3 |
