- LAMPS Light airborne multipurpose system.
- LANTIRN Low-altitude navigation and targeting infra-red, night.
- LAPES Low-altitude parachute extraction system.
- LBA Luftfahrtbundesamt (German civil aviation authority).
- lb Pound, non-SI unit of weight: 0.453592 kg.
- lb st Pounds of static thrust.
- LCD Liquid crystal display, used for showing instrument information.
- LCN Load classification number, measure of 'flotation' of aircraft landing gear linking aircraft weight, weight distribution, tyre numbers, pressures and disposition.
- LED Light-emitting diode.
- lift dumper Spoiler designed to open on landing to reduce lift and thus increase effectiveness of wheel braking.
- LINS Laser inertial navigation system.
- litre SI unit volume (0.264177 US gallon; 0.219975 Imp gallon).
- LLTV Low-light TV (thus, LLLTV, low-light level); see ALLTV.
- LO Low-observables, which see (stealth).
- load factor (1) Percentage of maximum payload; (2) design factor (g limit) for airframe.
- LOC Localiser (which see).
- localiser Element giving steering guidance in ILS.
- LOH Light observation helicopter.
- loiter Fly for maximum endurance, at much less than normal cruise speed.
- longerons Principal fore-and-aft structural members (for example in fuselage).
- Loran Long-range navigation; family of hyperbolic navaids based on ground radio emissions, now mainly Loran C.
- LOROP Long-range oblique photography.
- LOS Line of sight.
- low-observables Materials, structures and techniques designed to minimise aircraft signatures of all kinds.
- lox Liquid oxygen.
- LP Low pressure (LPC, compressor; LPT, turbine).
- LRIP Low-rate initial production.
- LRMTS Laser ranger and marked-target seeker.
- LRU Line-replaceable unit.
- Ltd Limited (company constitution).
