 | United Airlines | 1931 | 715 |
 | UPS Airlines | 1907 | 237 |
 | UTair | 1991 | 63 |
 | Ural Airlines | 1996 | 37 |
 | Ukraine International Airlines | 1992 | 35 |
 | Uzbekistan Airways | 1992 | 28 |
 | UNI Airways Corporation | 1998 | 17 |
 | Uni-Top Airlines | 2009 | 10 |
 | United Airways Bangladesh Ltd | 2005 | 8 |
 | Urumqi Airlines Co. Ltd. | 2014 | 6 |
 | UVT Aero | 2015 | 6 |
 | ULS Airlines Cargo | 2004 | 5 |
 | UM Air | 1998 | 2 |
 | USA Jet Airlines | 1994 | 1 |
| Urgemer Canarias | - | - |
| U S Army Parachute Team | - | - |
| UFS | - | - |
| U S Marshals Service, U.S. Department Of Justice | - | - |
| UAS/AEF Leuchars | - | - |
| Unifly | - | - |
| Ukraine Airalliance | - | - |
| UK Home Office | - | - |
| Ukraina Air Enterprise | - | - |
| Unidades Aeromoviles del Ejercito De Tierra | - | - |
| UN Humanitarian Relief Flights (Kosovo) | - | - |
| United Carriers Systems | - | - |
| Union de Transportes Aereo de Guinea Ecuatorial | - | - |
| United States Coast Guard Auxiliary | - | - |
| UK Royal / VIP Flights | - | - |
| UAS/AEF Church Fenton | - | - |
| Ultrair | - | - |
| US Army Aeronautical Services Agency | - | - |
| Unique Air Charter | - | - |
| United Caribbean Airlines | - | - |
| U Airlines | - | - |
 | US-Bangla Airlines | - | - |
| Universitetet I Tromso | - | - |
| Ulendo Airlink | - | - |
| Unsped Paket Servisi | - | - |
| US Jet | - | - |
| US Express | - | - |
| Uganda Royal Airways | - | - |
| University of North Dakota | - | - |
 | UK International Airlines | - | - |
| UAS/AEF St Athan | - | - |
 | United States Navy | - | - |
| UK Royal / H.R.H. Duke of York | - | - |
| United Nations | - | - |
| Ukrainian Helicopters | - | - |
 | UTair Express | - | - |
| United Africa Airline (Liberia) | - | - |
| Ultimate Heli | - | - |
| Union Des Transports Africains de Guinee | - | - |
| UAS / AEF Wyton | - | - |
| US Airports Air Charter | - | - |
 | Universal Airways, Inc. | - | - |
| Unicorn Air | - | - |
| Union Flights | - | - |
| Universal Airlines | - | - |
| Ulba | - | - |
| uSKY AIR | - | - |
| Uvavemex | - | - |
| Upper Area Control Centre | - | - |
| UAS/AEF Boscombe Down | - | - |
 | Unique Air | - | - |
| Ultimate Air | - | - |
| Universal Airlines | - | - |
| United States Air Force 100th Air Refueling Wing | - | - |
| Ultraair | - | - |
 | US Airways | - | - |
| United States Air Force 89th Airlift Wing | - | - |
| United Air Charters | - | - |
| Universal Aviation Academy | - | - |
| UAS/AEF Glasgow | - | - |
| Uganda Air Cargo | - | - |
| UK Royal Positioning Flights | - | - |
| US Department Of Justice Prisoner & Alien Transportation Service (JPATS) | - | - |
| United European Airlines | - | - |
| U.S. Department of the Interior, Office of Aircraft Services | - | - |
| US Immigration and Custom Enforcement | - | - |
| USAF Air Mobility Operations Control Center | - | - |
| United Aviation Services | - | - |
| UAS/AEF Leeming | - | - |
| UAS/AEF Benson | - | - |
| UAS/AEF Cosford | - | - |
 | Uniworld Air Cargo Corp. | - | - |
| Unidad de Helicopteros de la Ertzaintza | - | - |
| Ulyanovsk Higher Civil Aviation School | - | - |
| Ukrainian Handling Company | - | - |
| United Arab Emirates Air Force | - | - |
| U.S. Air Force Auxiliary/Civil Air Patrol | - | - |
 | Ultimate Jetcharters LLC dba Ultimate Air Shuttle | - | - |
| Unex - Universal Express Linhas Aereas | - | - |
| Universal Jet Rental de Mexico | - | - |
| UK Royal / VIP Flights | - | - |
| United Executive Jet | - | - |
| United Company for Aviation Administration | - | - |
| Ultimate Air Shuttle | - | - |
| U.S. Forest Service | - | - |
| University of Central Missouri | - | - |
| UAS/AEF Woodvale | - | - |
| UAS Cranwell | - | - |
| Uni-fly | - | - |
| University of Illinois Institute of Aviation | - | - |
| UK Royal VIP Helicopter Flights | - | - |
| United Arabian Airlines | - | - |
| U.S. Transportation Command | - | - |
| Ukrainian Pilot School | 1995 | - |