U
- Udet, Udet-Flugzeugbau GmbH – Germany
- Uetz, Walter Uetz Flugzeugbau – Switzerland
- UL-Jih, Kaplice, Czech Republic
- UFO, Ultimate Flying Object Inc – New Zealand
- Ullmann, Ullmann Aircraft Company – United States
- Ultimate, Ultimate Aircraft Division of Ultimate Aerobatics Ltd – Canada
- Ultravia, Ultravia Aero International Inc – Canada
- Umbaugh, Umbaugh Aircraft Corporation – United States
- Umbra, Aeronautica Umbra – Italy
- UNC, UNC Helicopter – United States
- Unikomtranso, Unikomtranso AO – Russia
- Unis, Unis Obchodni spol sro – Czech Republic
- United Canada, United Aircraft of Canada – Canada
- United Aircraft Corporation, United Aircraft Corporation – Russia
- United Consultant, United Consultant Corporation – United States
- UP International GmbH, Garmisch-Partenkirchen, Germany, formerly known as UP Europe, UP Products and Ultralite Products
- Urban, Urban Air sro – Czech Republic
- Utilicraft Aerospace Industries, Utilicraft Aerospace Industries – United States
- U-Turn GmbH, Villingen-Schwenningen, Germany
- UTVA, UTVA Fabrika Aviona – Yugoslavia, (1937–Present)
- UTVA, UTVA-Sour Metalne Industrije, RO Fabrika Aviona – Yugoslavia