| 1 | X | HONG KONG ISLANDS LINE AMERICA SA | | | PWRC |
| 2 | X1 | FORTHcrs SA | Designator X1 recalled by IATA. Computer Reservations Systems (CRS) | GR | AVCODES |
| 3 | X1 | Hahn Air Technologies GmbH | Computer Reservations Systems (CRS) | D | AVCODES |
| 4 | X18 | | | | TRAFFIC |
| 5 | X3 | Baikal Airlines | ICAO: BKL, Callsign: Baikal, | RUS | AVCODES |
| 6 | X3 | Hapag-Lloyd Express GmbH | ICAO: HLX, Callsign: Excellence, | D | AVCODES |
| 7 | X3 | Hapag-Lloyd Express GmbH | ICAO: HLX, Callsign: Yellow Smile, Merged into TUIFly GmbH. | D | AVCODES |
| 8 | X3 | TUIfly GmbH | ICAO: TUI, Callsign: Tuifly, IATA Prefix: 617, Name changed from Hapag Lloyd Fluggessellschaft mbH, ICAO callsign changed from Hapag Lloyd. IATA designator changed from HF w.e.f. 01 October 2010. ICAO designator changed from HLF w.e.f. 01 October 2010. | D | AVCODES |
| 9 | X36 | | | | TRAFFIC |
| 10 | X4 | Vanair Limited | Designator X4 recalled by IATA | VAN | AVCODES |
| 11 | X4 | BAS (H.K.) Limited | Designator X4* recalled by IATA | HK | AVCODES |
| 12 | X4 | XL Airways Germany GmbH | ICAO: GXL, Callsign: Stardust, Ceased operations on 14 December 2012. Filed for bankruptcy protection on 27 Dec 2012. | D | AVCODES |
| 13 | X4 | Air Excursions, LLC | Acquired by Alaska Seaplanes and merged in spring 2013. | USA | AVCODES |
| 14 | X4 | Air Excursions, LLC d/b/a Alaska Seaplanes | Acquired by Alaska Seaplanes and merged in spring 2013. | USA | AVCODES |
| 15 | X46 | | | | TRAFFIC |
| 16 | X5 | Cronus Airlines | ICAO: CUS, Callsign: Cronus, IATA designator X5 recalled due merger with Aegean Airlines S.A. A3/AEE | GR | AVCODES |
| 17 | X5 | aeronova S.L.U. d/b/a Air Europa Express | ICAO: OVA, Callsign: Aeronova, | E | AVCODES |
| 18 | X5 | Sunworld International Airlines, Inc. | ICAO: SWI, IATA designator changed to SM | USA | AVCODES |
| 19 | X5 | Trans Pacific Air (Malaysia) SDN. BHD. | IATA designator changed to 4H | MAL | AVCODES |
| 20 | X5 | Airdirect Bedarfsflug GmbH | ICAO: DRR, Callsign: Aerodirect, Designator X5* recalled by IATA | A | AVCODES |
| 21 | X5 | Afrique Airlines, S.A. | ICAO: FBN, Callsign: Afrique-Benin, Founded in 2002. Commenced operations in 2003. Ceased operations during 2006. | DY | AVCODES |
| 22 | X5 | ULD Logistics LLC | Designator X5* recalled by IATA. Non-Airline Unit Load Devices (ULD) companies | USA | AVCODES |
| 23 | X5 | S.C. Ten Airways S.R.L. | ICAO: OTJ, Callsign: Tender Air, | RO | AVCODES |
| 24 | X50 | | | | TRAFFIC |
| 25 | X55 | | | | TRAFFIC |
| 26 | X6 | Challenge Air Cargo Limited | ICAO: CHZ, Callsign: Cargo Rock, IATA Prefix: 752, | M | AVCODES |
| 27 | X7 | Zambia Skyways Ltd. | ICAO: ZAK, Callsign: Easair, Designator X7 recalled by IATA, ICAO designator changed from EAZ. Formerly Eastern Air Ltd. / IATA code changed from X7* | Z | AVCODES |
| 28 | X7 | Eastern Air Ltd. | ICAO: EAZ, Callsign: Easair, Named changed to Zambia Skyways | Z | AVCODES |
| 29 | X7 | Joint Stock Company Chitaavia | ICAO: CHF, Callsign: Chita, Designator X7 recalled by IATA | RUS | AVCODES |
| 30 | X7 | Zambia Skyways | ICAO: EAZ, Callsign: Easair, Formerly Eastern Air Ltd. / IATA code changed to X7 | Z | AVCODES |
| 31 | X7 | Zambia Skyways Ltd. | ICAO: EAZ, Callsign: Easair, Designator X7 reinstated by IATA, ICAO designator changed to ZAK. Formerly Eastern Air Ltd. / IATA code changed from X7* | Z | AVCODES |
| 32 | X7 | Air Service | Designator X7 reinstated by IATA | G | AVCODES |
| 33 | X7 | ACE Belgium Freighters S.A. | ICAO: FRH, Callsign: Ace Freight, IATA Prefix: 744, Name changed to Challenge Airlines (BE) S.A. | B | AVCODES |
| 34 | X7 | Challenge Airlines (BE) S.A. | ICAO: FRH, Callsign: Challenge, IATA Prefix: 744, ICAO Designator changed to CHG. Name changed from ACE Belgium Freighters S.A. | B | AVCODES |
| 35 | X7 | Challenge Airlines (BE) S.A. | ICAO: CHG, Callsign: Challenge, IATA Prefix: 744, ICAO Designator changed from FRH. Name changed from ACE Belgium Freighters S.A. | B | AVCODES |
| 36 | X8 | Federico II Airways, S.p.A. | ICAO: FDE, Callsign: Federeagle, IATA designator changed to 2D | I | AVCODES |
| 37 | X8 | Icaro S.A. | ICAO: ICD, Callsign: Icaro, IATA Prefix: 545, Founded in 1971. Ceased operations during 2011. | EC | AVCODES |
| 38 | X8 | Airmax S.A. | ICAO: MMX, Callsign: Perumax, IATA Prefix: 658, | PE | AVCODES |
| 39 | X9 | Khors Aircompany Ltd. | ICAO: KHO, Callsign: Aircompany Khors, IATA Prefix: 852, | UA | AVCODES |
| 40 | X9 | Landsflug ehf | ICAO: ISL, Name changed to City Star Airlines ehf | IS | AVCODES |
| 41 | X9 | City Star Airlines ehf | ICAO: ISL, Callsign: Islandia, Ceased operation on 30 January 2008. Designator X9 re-instated by IATA. Name changed from Landsflug ehf | IS | AVCODES |
| 42 | X9 | Joint Stock Company Avion Express | ICAO: NVD, Callsign: Nordvind, | LT | AVCODES |
| 43 | XA | ARINC (Aeronautical Radio, Inc.) | ICAO: XAA, Callsign: Rockfish, Comms org for airline industry | USA | AVCODES |
| 44 | XAA | ARINC (Aeronautical Radio, Inc.) | IATA: XA, Callsign: Rockfish, Comms org for airline industry | USA | AVCODES |
| 45 | XAA | Aeronautical Radio Inc | | | ICAO1 |
| 46 | XAAK | XAAK TRANSPORT INC | | | SCAC4 |
| 47 | XAB | Xabre Aerolineas, S.A. de C.V. | Callsign: Aero Xabre, | MEX | AVCODES |
| 48 | XAB | Xabre Aerolineas | | | ICAO1 |
| 49 | XAC | Air Charter World | | USA | AVCODES |
| 50 | XAC | Air Charter World | | | ICAO1 |
| 51 | XACU | ALPSCONTAINER | | D | BIC |
| 52 | XAD | Certified Aircraft Dispatch, Inc. | | USA | AVCODES |
| 53 | XAD | Certified Air Dispatch | | | ICAO1 |
| 54 | XAE | Xair Brno | Callsign: Aura, | CZ | AVCODES |
| 55 | XAF | Executive Air Fleet | | USA | AVCODES |
| 56 | XAF | Executive Air Fleet | | | ICAO1 |
| 57 | XAGU | XI'AN INTERNATIONAL PORT MULTIMODAL TRANSPORTATION CO.,LTD | | PRC | BIC |
| 58 | XAH | Executive Aircraft Services | | GB | AVCODES |
| 59 | XAH | Executive Aircraft Services | | | ICAO1 |
| 60 | XAI | Apex Air Co., Ltd. | Callsign: Pex Air, | PRC | AVCODES |
| 61 | XAK | Airkenya Express Ltd. | IATA: QP, IATA Prefix: 853, Name changed from Airkenya Aviation Ltd. d/b/a Regional Air. Formerly Airkenya Aviation Ltd. | EAK | AVCODES |
| 62 | XAK | Airkenya Express Ltd. | IATA: P2, IATA Prefix: 853, IATA Designator changed from QP. Designator reinstated by P2 IATA. Name changed from Airkenya Aviation Ltd. d/b/a Regional Air. Formerly Airkenya Aviation Ltd. | EAK | AVCODES |
| 63 | XAK | Airkenya | | | ICAO1 |
| 64 | XAL | Aerovias Xalitic. S.A. de C.V. | Callsign: Xalitic, | MEX | AVCODES |
| 65 | XAL | Airlines of Tasmania Pty Ltd. | ICAO designator changed to ATM | AUS | AVCODES |
| 66 | XAM | AMR Services Corp | Callsign: Alliance, | USA | AVCODES |
| 67 | XAM | AMR Services Corporation | | | ICAO1 |
| 68 | XANS | XAN SYSTEMS INC | | | SCAC4 |
| 69 | XANT | XPEDX TRANSPORTATION RICHMOND (DIV | | | SCAC4 |
| 70 | XANU | PETRO KIMIA NEGIN CO | | | SCAC4 |
| 71 | XAO | Airline Operations Services | | USA | AVCODES |
| 72 | XAO | Airline Operations Services | | | ICAO1 |
| 73 | XAP | Direct Air, Inc. d/b/a Midway Connection | Callsign: Mid-Town, | USA | AVCODES |
| 74 | XAP | Direct Air, Inc. | Callsign: Air Direct, | USA | AVCODES |
| 75 | XAP | Midway Connection | | | ICAO1 |
| 76 | XAPU | XI'AN FREE TRADE PORT CONSTRUCTION AND OPERATION CO.,LTD. | | PRC | BIC |
| 77 | XAR | PT. Travel Express Aviation Services d/b/a Xpress Air | IATA: XN, Callsign: Travel Express, Name change from PT. Travel Express Aviation Services d/b/a Express Air during 2012. | RI | AVCODES |
| 78 | XAR | PT. Travel Express Aviation Services d/b/a Express Air | IATA: XN, Callsign: Travel Express, Name changed to PT. Travel Express Aviation Services d/b/a xpressair during 2012. | RI | AVCODES |
| 79 | XAR | Travel Express Aviation Services | | | ICAO1 |
| 80 | XARU | OXYGEN & ARGON WORKS LTD | | IL | BIC |
| 81 | XAS | PHH Aviation Systems, Inc. | | USA | AVCODES |
| 82 | XAS | PHH Aviation System | | | ICAO1 |
| 83 | XAT | AT And T Aviation Division | | USA | AVCODES |
| 84 | XAT | AT and T Aviation Division | | | ICAO1 |
| 85 | XAU | Aerolink Uganda Limited | IATA: A8, Designator A8* recalled by IATA | EAU | AVCODES |
| 86 | XAU | Aerolink Uganda Limited | IATA: A8, Designator A8* reinstated by IATA | EAU | AVCODES |
| 87 | XAV | Aviaprom Enterprises | Callsign: Aviaprom, | RUS | AVCODES |
| 88 | XAV | Aviaprom Enterprises | | | ICAO1 |
| 89 | XAW | Zoom Airways Limited | IATA: 3Z, | BD | AVCODES |
| 90 | XAX | Airx Limited t/a Lecocqs.com | Callsign: Blue Island, Name changed to Airx Limited t/a Rockhopper | GB | AVCODES |
| 91 | XAX | Airx Limited t/a Rockhopper | Callsign: Blue Island, Name changed to Airx Limited t/a Blue Islands. Name changed from Airx Limited t/a Lecocqs.com | GB | AVCODES |
| 92 | XAX | Airasia X Berhad d/b/a Airasia X | IATA: D7, Callsign: Xanadu, IATA Prefix: 843, Name changed from Fly Asian Express Sdn Bhd | MAL | AVCODES |
| 93 | XAX | AirAsia X | | MAL | TRAFFIC |
| 94 | XB | International Air Transport Association | ICAO: IAT, Non-airline org. relating to the airline industry | CDN | AVCODES |
| 95 | XB | International Air Transport Association | ICAO: IAT, Billing and Settlement Plan. Non-airline org. relating to the airline industry | CDN | AVCODES |
| 96 | XB | International Air Transport Association | ICAO: IAT, Billing and Settlement Plan. Non-airline org. relating to the airline industry | CDN | AVCODES |
| 97 | XBAR | BAY AREA RAPID TRANSIT (BART) | | | PWRC |
| 98 | XBG | Bangor, City Of | | USA | AVCODES |
| 99 | XBG | City of Bangor | | | ICAO1 |
| 100 | XBO | Baseops International, Inc. | IATA: 3Y, | USA | AVCODES |
