K
- K & S, K & S Aircraft – Canada
- K & S, K & S Aircraft Supply – Canada
- Kader, Kader Aircraft Factory – Egypt
- Kaiser, Kaiser Flugzeugbau GmbH – Germany
- Laurent de Kalbermatten, Villars-sur-Glâne, Switzerland
- Kalinauskas, Rolandas Kalinauskas – Lithuania
- Kaman, Kaman Aerospace Corporation – United States
- Kaman, Kaman Aircraft Corporation – United States
- Kaman, Kaman Corporation – United States
- Kaminskas, Rim Kaminskas – United States
- Kamov, Kamov OAO – Russia
- Kamov, Kamov OKB – Russia
- Kamov, Vertoletyi Nauchno-Tekhnicheskiy Kompleks Imeni N. I. Kamova – Russia
- Kanpur, Indian Air Force, Aircraft Manufacturing Depot – India
- KARI, Korea Aerospace Research Institute – South Korea
- Kari-Keen, Kari-Keen Aircraft Inc – United States
- Kawanishi Aircraft Company, Kawanishi Aircraft Company – Japan
- Kawasaki, Kawasaki Heavy Industries Ltd – Japan
- Kawasaki, Kawasaki Jukogyo KK – Japan
- Kawasaki, Kawasaki Kokuki Kogyo K. K. – Japan
- Kayaba, Kayaba Industrial Co. – Japan
- Kazan, Kazansky Vertoletnyi Zavod AO – Russia
- KEA, Kratiko Ergostasio Aeroplanon – Greece (1925–present)
- Keleher, James J. Keleher – United States
- Kelly, Dudley R. Kelly – United States
- Kelowna, Kelowna Flightcraft Group – Canada
- Kestrel (1), Kestrel Aircraft Company – United States
- Kestrel (2), Kestrel Sport Aviation – Canada
- Keuthan, Keuthan Aircraft – United States, (?-1996) > Aero Adventure Aviation
- Keystone Aircraft Corporation, Keystone Aircraft Corporation – United States, (1920–1933) (Ogdensburg Aeroway Corp.) > Keystone-Loening > Curtiss-Wright
- Khrunichev, Gosudarstvennyi Kosmicheskii Nauchno-Proizvodstvennyi Tsentr Imeni M V Khrunicheva – Russia
- Kieger, André Kieger – France
- Killingsworth, Richard Killingsworth – United States
- Kimball, Jim Kimball Enterprises Inc – United States
- Kimball, Michael G. Kimbrel – United States
- Kimfly D.O.O., Vodice, Slovenia
- Kinetic, Kinetic Aviation Inc – United States
- King's, The King's Engineering Fellowship – United States
- Kjeller, Kjeller Flyvemaskinsfabrik – Norway
- Kingsbury Aviation. London, England
- Klemm, Hans Klemm Flugzeugbau – Germany, > Siebel
- Klemm, Klemm Leichtflugzeugbau GmbH – Germany
- Klemm, Klemm-Flugzeuge GmbH – Germany
- KLS Composites, KLS Composites – United States
- Kokusai, Kokusai – Japan
- Kolb, Kolb Aircraft Inc – United States
- Kolb, Kolb Company Inc – United States
- Kolb, The New Kolb Aircraft Company Inc – United States
- Kondor, Kondor – Germany
- Koolhoven, Koolhoven Aircraft – Netherlands
- Korea Aerospace, Korea Aerospace Industries Ltd – South Korea, (KAI)
- Korean Air, Korean Air Lines Company Ltd – South Korea
- Kovach-Elmendorf, Alexander Kovach and Leonard Elmendorf – United States
- Kovacs, Joseph Kovács – Brazil
- Kraft, Phil Kraft – United States
- Krasniye Kryl'ya – Taganrog, Russia
- Kress, Wilhelm Kress – Austria-Hungary
- Kreider-Reisner, Kreider-Reisner Aircraft Company Inc – United States
- Kyūshū Aircraft Company, Kyūshū Aircraft Company – Japan