| 1 | ZO | Ozark Air Lines, Inc. d/b/a/ Great Plains Airlines | ICAO: GRP, Callsign: Great Plains, Name changed from Ozark Air Lines, Inc. Founded in 2001. Ceased operations in 2004. ICAO designator changed from OZR | USA | AVCODES |
| 2 | ZO | Ozark Air Lines, Inc. | ICAO: OZR, Name changed to Ozark Air Lines, Inc. d/b/a Great Plains Airlines. ICAO designator changed to GRP | USA | AVCODES |
| 3 | ZO | Air Georgian Ltd. d/b/a Air Alliance | ICAO: GGN, Callsign: Georgian, IATA designator changed to ZX | CDN | AVCODES |
| 4 | ZO | Central Air Transpsort Services | ICAO: CEN, Callsign: Shumba, | ZW | AVCODES |
| 5 | ZO | M/S Zexus Air Services Pvt. Ltd t/a Zoom Air | ICAO: ZOM, Callsign: Zoom, Designator ZO recalled by IATA. DGCA licence approved. Commence domestic operations in February 2017. | IND | AVCODES |
| 6 | ZO | Colorful Yunnan General Aviation Co., Ltd. t/a Colorful Yunnan Airlines | | PRC | AVCODES |
| 7 | ZÖA | Zweckverband Öffentlicher Nahverkehr im Ammertal | Tübingen | D | privat-bahn.de |
| 8 | ZOB | Zollernbahn | | D | TRAFFIC |
| 9 | ZOBR | ZOBRIST, NEAL L INC | | | SCAC4 |
| 10 | ZOCC | OCCIDENTAL CHEMICAL | | | PWRC |
| 11 | ZOCI | ZOCALO IMPORTS INC | | | SCAC4 |
| 12 | ZOCO | ZIEGLER OIL CO | | | SCAC4 |
| 13 | ZODA | ZORMAN, DALE A TRUCKING SERVICE INC | | | SCAC4 |
| 14 | ZODY | ZODYS MOVING & STORAGE INC | | | SCAC4 |
| 15 | ZOES | ZOES TROPICALS INC | | | SCAC4 |
| 16 | ZOGJ | ZOT LUXURY LOGISTICS INC | | | SCAC4 |
| 17 | ZOIC | ZOLLICKER OIL CO INC | | | SCAC4 |
| 18 | ZOLA | ZOLA ENTERPRISES CO LTD | | | SCAC4 |
| 19 | ZOM | M/S Zexus Air Services Pvt. Ltd t/a Zoom Air | IATA: ZO, Callsign: Zoom, Designator ZO recalled by IATA. DGCA licence approved. Commence domestic operations in February 2017. | IND | AVCODES |
| 20 | ZOM | M/S Zexus Air Services Pvt. Ltd t/a Zoom Air | Callsign: Zoom, Designator ZO recalled by IATA. DGCA licence approved. Commence domestic operations in February 2017. | IND | AVCODES |
| 21 | ZOMA | ZODIAC MARITIME AGENCIES LTD | | | SCAC4 |
| 22 | ZOMT | ZOOM TRANSPORT INC | | | SCAC4 |
| 23 | ZONT | ZONE TRANSPORTATION COMPANY | | | SCAC4 |
| 24 | ZOOK | ZOOK TRUCKING LLC | | | SCAC4 |
| 25 | ZOS | ZOS Zvolen s.r.o. | | SK | TRAFFIC |
| 26 | ZOS | ZOS ZVOLEN s.r.o. | | SK | VKM |
| 27 | ZOSTT | ŽOS Trnava, a.s. | | SK | VKM |
| 28 | ZOSVR | ŽOS Vrútky a.s. | | SK | VKM |
| 29 | ZOSZV | Železničné opravovne a strojárne Zvolen, a.s. | | SK | VKM |
| 30 | ZOUD | ZOUDIS, PANAYOTE | | | SCAC4 |
| 31 | ZOYA | ZOYA VENTURES | | | SCAC4 |
