L
- Liaoning Ruixiang General Aviation Manufacture Company Limited, Shenyang, China
- La France, Neil La France – United States
- Laird, E. M. Laird Airplane Company – United States
- Lake, A.E.R.O. Aircraft Services, LLC [1] – United States
- Lake, Lake Aircraft Corporation – United States
- Lake, Lake Aircraft Division of Consolidated Aeronautics Inc. – United States
- Lake, Lake Aircraft Inc. – United States
- Lake, Lake Amphibian Inc. – United States
- Lambert, Lambert Aircraft Engineering bvba – Belgium
- Lammer Geyer, Lammer Geyer Aviation – South Africa
- Lancair, Lancair Group Inc – United States
- Lancair, Lancair International Inc – United States
- Lancashire, Lancashire Aircraft Company Ltd – United Kingdom
- Larkin Aircraft, Larkin Aircraft Supply Co. – Australia, (LASCO)
- Laser, Laser Aerobatics – Australia
- Latécoère, Société Industrielle d'Aviation Latécoère – France
- Laven, Joe Laven – United States
- Laverda, Laverda SpA – Italy
- LAVIASA, Latinoamericana de Aviación S.A. – Argentina
- Lavochkin, Lavochkin (OKB-301) – Russia
- Layzell Gyroplanes – Quedgeley, Gloucester, UK
- Leading Edge Air Foils, Lyons, Wisconsin, United States
- Lear, Lear Inc – United States
- Learjet, Bombardier Aerospace Learjet – United States
- Learjet, Learjet Corporation – United States, (?-1990) > Bombardier Aerospace
- Learjet, Learjet Industries Inc – United States
- Learjet, Learjet Corporation – United States
- Learjet, Learjet Inc – United States
- Leavens, Leavens Brothers Ltd – Canada
- Lederlin, François Lederlin – France
- Legend, Legend Aircraft Inc – United States
- Leger Aviation, Archiac, France
- Leger, Gilles Leger – Canada
- LeO, Lioré et Olivier – France
- Les Mureaux – see ANF Mureaux
- Let, Let Národní Podnik – Czechoslovakia
- Let, Let AS – Czech Republic
- Letov, Letov – Czechoslovakia
- Levasseur, Pierre Levasseur – France
- Levy, Constructions Aeronautiques J. Levy – France
- Leza AirCam Corporation — see Lockwood Aircraft
- Leza-Lockwood — see Lockwood Aircraft
- Liberty (1), Liberty Aeronautical – United States
- Liberty (2), Liberty Aerospace Inc – United States
- Lichtwerk, NV Lichtwerk – Netherlands
- Light Aero, Light Aero Inc – United States
- Light Miniature Aircraft, Okeechobee, Florida, United States
- Light Wing, Light Wing AG – Switzerland
- Lightning Bug, Lightning Bug Aircraft Corporation – United States
- Lilienthal, Otto Lilienthal – Germany
- Linke-Hofmann, Linke-Hofmann Werke A. G. – Germany
- Lipnur, Lembaga Industri Penerbangan Nurtanio – Indonesia
- Lisunov, Lisunov OKB – Russia
- Liteflite, Botany, New South Wales, Australia
- LiteWing Aircraft, Caryville, Tennessee, United States
- Little Wing Autogyros, Inc., Mayflower, Arkansas, United States
- Lmaasa, Lockheed Martin Aircraft Argentina SA – Argentina
- Load Ranger, Load Ranger Inc – United States
- Lockheed Corporation – United States, (1912–1996) > Lockheed Martin
- Lockheed Martin, Lockheed Martin Corporation – United States, (1996–present)
- Lockheed Martin-Boeing, see Lockheed Martin and Boeing – United States
- Lockheed-Azcarate, Lockheed-Azcarate SA – Mexico, (LASA)
- Lockheed-Boeing, see Lockheed and Boeing – United States
- Lockheed-Kaiser, Avions Lockheed-Kaiser – Argentina
- Lockwood Aircraft Corporation — United States
- Loehle, Loehle Aircraft Corporation – United States
- Loening Aeronautical, Loening Aircraft Co. Inc. – United States, (Loening Aeronautical Engineering Corp. or Grover Loening Aircraft Co. Inc.)
- Lohner, Jacob Lohner Werke und Sohn – Austria-Hungary
- Loire, Loire – France
- Lombardi, Aeronautica Lombardi – Italy
- Lombardi, Francis Lombardi & Companie – Italy
- Long, David Long – United States
- Longren, Longren Aircraft Company Inc – United States
- Lopresti, LoPresti Inc – United States
- Loravia, Lorraine Aviation – France
- Lowe, Willard & Fowler Engineering Company
- Letecké Opravovne Trencin SP|LOT, Letecké Opravovne Trencin SP – Slovakia
- Loving-Wayne, Neal V. Loving, Wayne Aircraft Company – United States
- LTV, Ling-Temco-Vought Inc – United States
- LTV, LTV Aerospace Corporation – United States
- Lualdi-Tassotti, Lualdi-Tassotti – Italy
- Lübeck-Travemünde, Flugzeugwerft Lübeck-Travemünde GmbH – Germany, (1914–?)
- Lucas, Emile Lucas – France
- Luftfahrzeug-Gesellschaft m.b.H. (LFG), Germany, airships 1909–1932, aeroplanes 1915–1933
- Luftschiffbau Schütte-Lanz, Germany, rigid airships 1909–1917, aeroplanes 1915–1918
- Luftverkehrsgesellschaft m.b.H., Berlin-Johannisthal – Germany
- Lunds Tekniske, Lunds Tekniske – Norway
- Lundy, Brian Lundy – United States
- Luscombe, Luscombe Aircraft Corporation – United States
- Luscombe, Luscombe Airplane Corporation – United States
- Luscombe, Luscombe Airplane Development Corporation – United States
- Luton, Luton Aircraft Ltd – United Kingdom
- LWD, Lotnicze Warsztaty Doświadczalne – Poland, (Experimental Aviation Workshops)
- LWS, Lubelska Wytwórnia Samolotów – Poland, (Lublin Aircraft Factory)
- Lyavin, Peter Lyavin – Russia