| Known As / Full Name |
URL |
| U Airlines / U Airlines Co. Ltd. | www.u-airlines.com |
| U.S. Air Force Auxiliary/Civil Air Patrol / U.S. Air Force Auxiliary/Civil Air Patrol | www.gocivilairpatrol.com |
| U.S. Department of Interior / U.S. Department of Interior | www.doi.gov |
| U.S. Department of State, INL Air Wing / U.S. Department of State, International Narcotics and Law Enforcement Affairs (INL Air Wing) | www.state.gov/aviation-support |
| U.S. Forest Service / U.S. Forest Service | www.fs.fed.us |
| U.S. Transportation Command / U.S. Transportation Command | www.transcom.mil |
| UAS Cranwell / UAS Cranwell | www.raf.mod.uk/rafcollegecranwell/ |
| UBM Aviation - OAG / UBM Aviation - OAG | www.ubm.com |
| uep Airways / uep Airways | www.uepfly.com |
| Uganda Airlines / Uganda National Airlines Company Limited d/b/a/ Uganda Airlines | ugandaairlines.com |
| UK Royal Positioning Flights / UK Royal Positioning Flights (in military aircraft) | www.raf.mod.uk |
| Ukraine Air Enterprise / Ukraine Air Enterprise | www.saeukraine.org.ua |
| Ukraine International Airlines / Private Stock Company "Ukraine International Airlines" | www.flyuia.com |
| Ukraine-Airalliance / PJSC Ukraine-Airalliance | www.uaa-avia.com |
| Ukrainian Helicopters / Aviation Company Ukrainian Helicopters | ukrcopter.com |
| Ukrainian Wings / Ukrainian Wings | www.uawings.com |
| ULS Airlines Cargo / ULS Havayollair Kargo Tasimacilik A.S. | ulsairlines.com |
| Ulster Flying Club / Ulster Flying Club (1981) | www.ulsterflyingclub.co.uk |
| Ultimate Air Shuttle / Ultimate Jetcharters LLC dba Ultimate Air Shuttle | www.ultimateairshuttle.com |
| Ultimate Airways / Ultimate Airways (Pty) Ltd | ultimate-aviation.net |
| Ultimate Heli / Ultimate Heli (Pty) Ltd | ultimate-aviation.net |
| umzaXpress / Umza Aviation Services Limited d/b/a umzaXpress | www.umzaxpress.com |
| UNI Airways / UNI Airways Corporation | www.uniair.com.tw |
| Unicair / Unicair GmbH | www.unicair.eu |
| Unicorn Air / Unicorn Air Charter Services | www.flyunicornair.com |
| Uni-fly / Uni-fly A/S | www.uni-fly.dk |
| Unilode Aviation Solutions / Unilode Aviation Solutions Netherlands BV | www.unilode.com |
| Unilode Aviation Solutions / Unilode Aviation Solutions New Zealand Limited | www.unilode.com |
| Unilode Aviation Solutions Switzerland / Unilode Aviation Solutions Switzerland Ltd. | www.unilode.com |
| Union Aviation / AS Union Aviation | www.unionaviation.aero |
| Unique Air / Unique Air FZE | uniqueair.ae |
| United Airlines / United Airlines, Inc. | www.united.com |
| United Aviate Academy / Westwind School of Aeronautics, Phoenix, LLC d/b/a United Aviate Academy | unitedaviate.com |
| United Eagle / United Eagle d.o.o. | eagleexpress.ch |
| United Nigeria Airlines / United Nigeria Airlines Company Limited | flyunitednigeria.com |
| United States Air Force 89th Airlift Wing / United States Air Force 89th Airlift Wing | www.andrews.af.mil |
| United States Government, Federal Aviation Administration / United States Government, Federal Aviation Administration | www.faa.gov |
| Universal Air / Universal Air Charter and Management Limited | universalair.aero |
| Universitetet I Tromso / Universitetet I Tromso | uit.no |
| University of Central Missouri / University of Central Missouri | www.ucmo.edu |
| Uniworld Air Cargo / Uniworld Commercial Group, S.A. (Uniworld Air Cargo) | www.uniworldaircargo.com |
| Up / Up | flyup.com |
| UPS / United Parcel Service Company (UPS) | www.ups.com |
| Ural Airlines / Ural Airlines | www.uralairlines.com |
| Urumqi Airlines / Urumqi Airlines Co. Ltd. | www.urumqi-air.com |
| US Army Aeronautical Services Agency / US Army Aeronautical Services Agency | www.usaasa.tradoc.army.mil |
| US Department Of Justice Prisoner & Alien Transportation Service (JPATS) / US Department Of Justice Prisoner & Alien Transportation Service (JPATS) | www.usmarshals.gov/jpats/ |
| US Immigration and Custom Enforcement / US Immigration and Custom Enforcement | www.ice.gov |
| USA Jet Airlines / USA Jet Airlines, Inc. | www.usajet.aero |
| USAC Airways 695 / USAC Airways 695, LLC d/b/a Aero | www.aero.com |
| US-Bangla Airlines / US-Bangla Airlines Limited | www.us-banglaairlines.com |
| USC / USC GmbH | usc.aero |
| uSKY AIR / uSKY AIR | eng.uskyair.com |
| Utair Aviation / Utair Aviation Joint-Stock Company | www.utair.ru |
| UTair-Helicopter Services / UTair-Helicopter Services | heli.utair.ru |
| UVT aero / JSC UVT aero | uvtaero.ru |
| UZ Aero Tech Group / UZ Aero Tech Group | uatgroup.uz |
| Uzbekistan Airways / Uzbekistan Airways Joint Stock Company | www.uzairways.com |