| UES Avia Aircompany | UES | ||
| Uganda Air Cargo | UCC | ||
| Uganda Airlines | QU | UGA | 673 |
| Ukhta Airenterprise | UKH | ||
| Ukraine Air Alliance Airlines | XH | UKL | |
| Ukraine Air Service | ASG | ||
| Ukraine International Airlines | PS | AUI | 566 |
| Ukrainian Cargo Airways | 6Z | UKS | |
| Ulyanovsk Civil Aviation Flight School | UHS | ||
| UM Air | UF | UKM | 828 |
| UNI Air | B7 | UIA | 525 |
| United Airlines Cargo | UA | UAL | 016 |
| United Arabian Airlines | UAB | ||
| United Eagle Airlines | EU | UEA | |
| United Parcel Service | 5X | UPS | 406 |
| Unsped Cargo Airlines | UNS | ||
| Ural Air | URW | ||
| Ural Airlines | U6 | SVR | 262 |
| Uralaviali | URL | ||
| Uralinteravia | U3 | URA | 713 |
| US Airways | US | USA | 037 |
| USA Jet Airlines | 0O | JUS | |
| USAfrica | E8 | USF | |
| UT Air | UT | TMN | |
| Uzbekistan Airways | HY | UZB | 250 |