| X2 | CXH | Xinhua Airlines | |
| X3 | BKL | 483 | Baikal |
| X4 | Vanair | ||
| X5 | CUS | Cronus Airlines | |
| X7 | CHF | 637 | Chita Avia |
| X8 | 545 | Icaro | |
| X9 | OAE | Omni Air Express | |
| X9 | ISL | City Star Airlines | |
| X9 | KHO | 852 | Khors Aircompany |
| XC | CLT | 918 | Air Caribbean |
| XC | KDC | KD Air Corporation | |
| XE | SCA | 301 | South Central Air |
| XF | VLK | 277 | Vladivostok Air |
| XG | NAO | 455 | North American Airlines |
| XH | TIT | Titan Cargo Airlines | |
| XH | UKL | Ukraine Air Alliance Airlines | |
| XJ | MES | 582 | Mesaba Aviation |
| XK | CCM | 146 | Compagnie Corse Mediterranee |
| XM | XME | 524 | Australian Air Express |
| XM | SMX | Alitalia Express | |
| XO | LTE | LTE International Airways | |
| XO | CXJ | 651 | Xinjiang Airlines |
| XP | CXP | Casino Express | |
| XQ | SXS | 564 | Sunexpress Air |
| XR | OZW | 674 | Skywest Airlines |
| XT | AXL | 824 | KLM Exel |
| XU | AXK | African Express Airways | |
| XX | WPL | 624 | Aeronaves del Peru |
| XZ | EXY | 83 | South African Express Airways |