| 1 | UK | KLM uk Ltd. | ICAO: UKA, Callsign: Ukay, IATA Prefix: 130, Name changed to Buzzaway Limited. Name changed from Air Uk Ltd. | GB | AVCODES |
| 2 | UK | Air Uk Ltd. | ICAO: UKA, Callsign: Ukay, IATA Prefix: 130, Name changed to KLM uk Ltd. | GB | AVCODES |
| 3 | UK | British Island Airways Ltd. (BIA) | Callsign: Britisland, IATA designator changed to KD | GB | AVCODES |
| 4 | UK | Buzzaway Limited | ICAO: UKA, Callsign: Ukay, IATA Prefix: 130, Name changed from KLM uk Ltd. Application for AOC withdrawn. Name changed from Air Uk Ltd. | GB | AVCODES |
| 5 | UK | TATA SIA Airlines Limited t/a Vistara | ICAO: VTI, Callsign: Vistara, IATA Prefix: 228, Joint venture between India's Tata Sons and Singapore Airlines. | IND | AVCODES |
| 6 | UKA | KLM uk Ltd. | IATA: UK, Callsign: Ukay, IATA Prefix: 130, Name changed to Buzzaway Limited. Name changed from Air Uk Ltd. | GB | AVCODES |
| 7 | UKA | Air Uk Ltd. | IATA: UK, Callsign: Ukay, IATA Prefix: 130, Name changed to KLM uk Ltd. | GB | AVCODES |
| 8 | UKA | Buzzaway Limited | IATA: UK, Callsign: Ukay, IATA Prefix: 130, Name changed from KLM uk Ltd. Application for AOC withdrawn. Name changed from Air Uk Ltd. | GB | AVCODES |
| 9 | UKA | Aero Flightops UK Limited | IATA: FO, Callsign: Black Jet, | GB | AVCODES |
| 10 | UKA | Buzzaway Limited | | | ICAO1 |
| 11 | UKFI | UNIK FORWARDING INC | | | SCAC4 |
| 12 | UKI | UK International Airlines Ltd | Callsign: Khaliq, ICAO Callsign changed to Magenta | GB | AVCODES |
| 13 | UKI | UK International Airlines Ltd | Callsign: Magenta, ICAO Callsign changed from Khaliq | GB | AVCODES |
| 14 | UKI | UK International Airlines | | | ICAO1 |
| 15 | UKIC | UR-KI INC | | | SCAC4 |
| 16 | UKKX | United Carbon Co. | 7/1930-1/1941 | | NAKINA |
| 17 | UKKX | United Carbon Co. | Apr-38 | | NRHS |
| 18 | UKKX | UNITED CARBON CO. | | | PWRC |
| 19 | UKL | PJSC Ukraine-Airalliance | Callsign: Ukraine Alliance, IATA Prefix: 271, Founded in 1992. | UA | AVCODES |
| 20 | UKL | Air UK Leisure Ltd. | IATA: MV, Callsign: Leisure, Name changed to Leisure International Airways on 01 May 1997. | GB | AVCODES |
| 21 | UKL | Ukraine Air Alliance | | | ICAO1 |
| 22 | UKM | Ukrainian Mediterranean Airlines Ltd. | IATA: UF, Callsign: Ukraine Mediterranee, IATA Prefix: 828, | UA | AVCODES |
| 23 | UKM | Ukraine Mediterranean Airlines Ltd t/a UM Air Airlines | IATA: UF, Callsign: Ukraine Mediterranee, IATA Prefix: 828, Ceased operation during 2018. | UA | AVCODES |
| 24 | UKM | UM Airlines | IATA: UF | | ICAO1 |
| 25 | UKMI | ULJANIK SHIPMANAGEMENT INC | | | SCAC4 |
| 26 | UKMU | Ukmergės autobusų parkas | | LT | TRAFFIC |
| 27 | UKN | Ukraine Air Enterprise | Callsign: Enterprise Ukraine, | UA | AVCODES |
| 28 | UKN | Ukraine Air Enterprise | | | ICAO1 |
| 29 | UKO | Yukos | Callsign: Yukos Bulgaria, Name changed to Naftex Bulgaria Holding | BG | AVCODES |
| 30 | UKO | Naftex Bulgaria Holding | Callsign: Naftex Bulgaria, Name changed from Yukos. Ceased operations. | BG | AVCODES |
| 31 | UKP | UK Home Office | Callsign: Police, | GB | AVCODES |
| 32 | UKP | United Kingdom Home Office | | | ICAO1 |
| 33 | UKR | Air Ukraine | IATA: 6U, Callsign: Air Ukraine, IATA Prefix: 891, Founded in 1992. Suspended operations in 2002. AOC revoked in 2004. | UA | AVCODES |
| 34 | UKR | Air Ukraine | IATA: 6U | | ICAO1 |
| 35 | UKRU | SETTI | | UA | BIC |
| 36 | UKS | Ukrainian Cargo Airways | IATA: 6Z, Callsign: Cargotrans, IATA Prefix: 516, Designator 6Z* recalled by IATA | UA | AVCODES |
| 37 | UKS | Ukrainian Cargo Airways | IATA: 6Z | | ICAO1 |
| 38 | UKT | Atlantic Bridge Aviation Ltd. | Callsign: Cloud, | GB | AVCODES |
| 39 | UKT | UKTUS, Aircompany | Callsign: Uktus, | RUS | AVCODES |
| 40 | UKTC | UK TRUCKING LLC | | | SCAC4 |
| 41 | UKTL | UNITED KING TRANSPORT LTD | | | SCAC4 |
| 42 | UKTN | UNIK TRANSPORTATION LLC | | | SCAC4 |
| 43 | UKU | Second Sveridlovsk Air Enterprise | Callsign: Pyshma, | RUS | AVCODES |
| 44 | UKU | Second Sverdlovsk Air Enterprise | | | ICAO1 |
| 45 | UKW | Lviv Airlines | IATA: 5V, Callsign: Ukraine West, IATA Prefix: 062, Ceased operations. Founded in 1992. | UA | AVCODES |
| 46 | UKW | Lviv Airlines | IATA: 5V | | ICAO1 |
| 47 | UKZ | Zoom Airlines Ltd | IATA: ZX, Callsign: Flyzoom, | GB | AVCODES |
