| 1 | ZK | Great Lakes Aviation Ltd. | ICAO: GLA, Callsign: Lakes Air, IATA Prefix: 846, Ceased operations on 26 March 2018. | USA | AVCODES |
| 2 | ZK | Zetavia Limited, Aircompany | ICAO: ZAV, Callsign: Zetavia, IATA Prefix: 686, | UA | AVCODES |
| 3 | ZKAT | ZTP Katowice | | PL | TRAFFIC |
| 4 | ZKCC | XTRA INTERMODAL | | | PWRC |
| 5 | ZKCC | XTRA Intermodal | | | RSRV |
| 6 | ZKET | ZKE TRANSPORTATION LOGISTICS LLC | | | SCAC4 |
| 7 | ZKLE | ZAKLEE INTERNATIONAL CORPORATION | | | SCAC4 |
| 8 | ZKLG | ZK LOGISTICS | | | SCAC4 |
| 9 | ZKMC | ZOOK MOLASSES CO | | | SCAC4 |
| 10 | ZKMH | Zakład Komunikacji Miejskiej w Hajnówce | City: Gdansk | PL | TRAFFIC |
| 11 | ZKPME | Zaporizhia Municipal Electric Transport Company "Zaporizhelektrotrans" | City: Zaporizhia | UA | TRAFFIC |
| 12 | ZKPSL | Zakład Komunikacji Publicznej Suchy Las | | PL | TRAFFIC |
| 13 | ZKRE | ZKR EXPRESS INC | | | SCAC4 |
| 14 | ZKSZCZY | Zaklad Komunikacji Miejskiej, sp. z o. o. | City: Szczytno | PL | TRAFFIC |
| 15 | ZKTP | Z K TRANSPORT INC | | | SCAC4 |
| 16 | ZKV | Transcaucus Railway | | RUE | TRAFFIC |
