| UAB | United Arabian Airlines | ||
| UAE | EK | 176 | Emirates SkyCargo |
| UAG | Afra Air Cargo Inc | ||
| UAK | Kiev Aviation Plant | ||
| UAL | UA | 016 | United Airlines Cargo |
| UAN | Aviaton | ||
| UAR | Aerostar | ||
| UBA | 8M | 599 | Myanmar Airways International |
| UCA | Commutair | ||
| UCC | Uganda Air Cargo | ||
| UDC | 7D | 897 | Donbassaero |
| UDD | 5D | 945 | Donbass Airlines |
| UDN | Z6 | 181 | Dniproavia Joint Stock Aviation Company |
| UEA | EU | United Eagle Airlines | |
| UES | UES Avia Aircompany | ||
| UGA | QU | 673 | Uganda Airlines |
| UGX | East African Airlines | ||
| UHS | Ulyanovsk Civil Aviation Flight School | ||
| UIA | B7 | 525 | UNI Air |
| UKA | UK | 130 | KLCuk |
| UKH | Ukhta Airenterprise | ||
| UKL | XH | Ukraine Air Alliance Airlines | |
| UKM | UF | 828 | UM Air |
| UKR | 6U | 891 | Air Ukraine |
| UKS | 6Z | Ukrainian Cargo Airways | |
| UKW | 5V | Lviv Airlines | |
| ULA | OD | 822 | Zuliana de Aviacion |
| UMK | Yuzmashavia | ||
| UNS | Unsped Cargo Airlines | ||
| UPA | GS | Air Foyle Heavylift | |
| UPS | 5X | 406 | United Parcel Service |
| URA | U3 | 713 | Uralinteravia |
| URG | 3N | Air Urga | |
| URJ | 6S | Star Air Aviation | |
| URL | Uralaviali | ||
| URN | 3T | 359 | Turan Air |
| URW | Ural Air | ||
| USA | US | 037 | US Airways |
| USC | AirNet Express | ||
| USF | E8 | USAfrica | |
| UTR | Aerotrans Airlines (Ukraine) | ||
| UYC | UY | 604 | Cameroon Airlines |
| UZB | HY | 250 | Uzbekistan Airways |
| UZS | C7 | 732 | Samarkand Airways |